mirror of
https://github.com/sigmasternchen/php-doc-en
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d00d946cb5
4.0.8 -> 4.2.0 git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@60091 c90b9560-bf6c-de11-be94-00142212c4b1
1346 lines
38 KiB
XML
1346 lines
38 KiB
XML
<?xml encoding="iso-8859-1"?>
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<!-- $Revision: 1.73 $ -->
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<reference id="ref.var">
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<title>Variable Functions</title>
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<titleabbrev>Variables</titleabbrev>
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<refentry id="function.doubleval">
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<refnamediv>
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<refname>doubleval</refname>
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<refpurpose>Alias of <function>floatval</function></refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>
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This function is an alias of <function>floatval</function>.
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</para>
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<note>
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<para>
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This alias is a left-over from a function-renaming. In older versions of
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PHP you'll need to use this alias of the <function>floatval</function>
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function, because <function>floatval</function> wasn't yet available in
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that version.
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</para>
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</note>
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</refsect1>
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</refentry>
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<refentry id="function.empty">
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<refnamediv>
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<refname>empty</refname>
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<refpurpose>Determine whether a variable is set</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>boolean <function>empty</function></funcdef>
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<paramdef>mixed <parameter>var</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<note>
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<para>
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<function>empty</function> is a language construct.
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</para>
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</note>
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<para>
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This is the opposite of
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<literal>(boolean) <parameter>var</parameter></literal>,
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except that no warning is generated when the variable is not set.
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See <link linkend="language.types.boolean.casting">converting
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to boolean</link> for more information.
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</para>
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<!-- Returns &false; if <parameter>var</parameter> is set and has a
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non-empty or non-zero value; &true; otherwise. -->
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<informalexample>
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<programlisting role="php">
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$var = 0;
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if (empty($var)) { // evaluates true
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echo '$var is either 0 or not set at all';
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}
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if (!isset($var)) { // evaluates false
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echo '$var is not set at all';
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}
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</programlisting>
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</informalexample>
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<simpara>
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Note that this is meaningless when used on anything which isn't a
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variable; i.e. <command>empty (addslashes ($name))</command> has
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no meaning since it would be checking whether something which
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isn't a variable is a variable with a &false; value.
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<!-- will even result in parse error (at least in PHP 4) -->
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</simpara>
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<simpara>
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See also <function>isset</function> and
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<function>unset</function>.
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</simpara>
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</refsect1>
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</refentry>
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<refentry id="function.floatval">
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<refnamediv>
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<refname>floatval</refname>
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<refpurpose>Get float value of a variable</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>float <function>floatval</function></funcdef>
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<paramdef>mixed <parameter>var</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<simpara>
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Returns the <type>float</type> value of <parameter>var</parameter>.
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</simpara>
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<para>
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<parameter>Var</parameter> may be any scalar type. You cannot use
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<function>floatval</function> on arrays or objects.
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<informalexample>
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<programlisting role="php">
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$var = '122.34343The';
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$float_value_of_var = floatval ($var);
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print $float_value_of_var; // prints 122.34343
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</programlisting>
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</informalexample>
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</para>
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<simpara>
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See also <function>intval</function>,
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<function>strval</function>, <function>settype</function> and
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<link linkend="language.types.type-juggling">Type
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juggling</link>.
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</simpara>
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</refsect1>
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</refentry>
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<refentry id="function.gettype">
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<refnamediv>
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<refname>gettype</refname>
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<refpurpose>Get the type of a variable</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>string <function>gettype</function></funcdef>
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<paramdef>mixed <parameter>var</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<para>
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Returns the type of the PHP variable
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<parameter>var</parameter>.
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</para>
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<warning>
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<simpara>
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Never use <function>gettype</function> to test for a certain type,
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since the returned string may be subject to change in a future version.
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In addition, it is slow too, as it involves string comparision <!--
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where's my dictionary? -->.
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</simpara>
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<simpara>
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Instead, use the <literal>is_*</literal> functions.
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</simpara>
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</warning>
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<para>
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Possibles values for the returned string are:
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<itemizedlist>
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<listitem>
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<simpara>"<type>boolean</type>" (since PHP 4)</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>integer</type>"</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>double</type>" (for historical reasons "double" is
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returned in case of a <type>float</type>, and not simply
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"float")</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>string</type>"</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>array</type>"</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>object</type>"</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>resource</type>" (since PHP 4)</simpara>
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</listitem>
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<listitem>
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<simpara>"<type>null</type>" (since PHP 4)</simpara>
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</listitem>
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<listitem>
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<simpara>"user function" (PHP 3 only, deprecated)</simpara>
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</listitem>
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<listitem>
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<simpara>"unknown type"<!-- someone's joking? --></simpara>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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For PHP 4, you should use <function>function_exists</function> and
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<function>method_exists</function> to replace the prior usage of
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<function>gettype</function> on a function.
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</para>
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<para>
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See also
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<function>settype</function>,
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<function>is_array</function>,
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<function>is_bool</function>,
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<function>is_float</function>,
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<function>is_integer</function>,
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<function>is_null</function>,
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<function>is_numeric</function>,
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<function>is_object</function>,
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<function>is_resource</function>,
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<function>is_scalar</function> and
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<function>is_string</function>.
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</para>
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</refsect1>
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</refentry>
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<refentry id="function.get-defined-vars">
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<refnamediv>
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<refname>get_defined_vars</refname>
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<refpurpose>
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Returns an array of all defined variables
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</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>array <function>get_defined_vars</function></funcdef>
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<void/>
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</funcprototype>
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</funcsynopsis>
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<para>
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This function returns an multidimensional array containing a list of
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all defined variables, be them environment, server or user-defined
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variables.
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<informalexample>
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<programlisting role="php">
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$b = array(1,1,2,3,5,8);
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$arr = get_defined_vars();
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// print $b
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print_r($arr["b"]);
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// print path to the PHP interpreter (if used as a CGI)
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// e.g. /usr/local/bin/php
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echo $arr["_"];
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// print the command-line paramaters if any
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print_r($arr["argv"]);
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// print all the server vars
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print_r($arr["HTTP_SERVER_VARS"]);
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// print all the available keys for the arrays of variables
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print_r(array_keys(get_defined_vars()));
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</programlisting>
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</informalexample>
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</para>
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<para>
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See also <function>get_defined_functions</function>.
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</para>
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</refsect1>
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</refentry>
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<refentry id="function.get-resource-type">
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<refnamediv>
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<refname>get_resource_type</refname>
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<refpurpose>
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Returns the resource type
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</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>string <function>get_resource_type</function></funcdef>
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<paramdef>resource <parameter>$handle</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<para>
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This function returns a string representing the type of the
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<type>resource</type> passed to it. If the paramater is not a
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valid <type>resource</type>, it
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generates an error.
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<informalexample>
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<programlisting role="php">
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$c = mysql_connect();
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echo get_resource_type($c)."\n";
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// prints: mysql link
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$fp = fopen("foo","w");
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echo get_resource_type($fp)."\n";
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// prints: file
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$doc = new_xmldoc("1.0");
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echo get_resource_type($doc->doc)."\n";
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// prints: domxml document
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</programlisting>
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</informalexample>
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</para>
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</refsect1>
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</refentry>
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<refentry id="function.intval">
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<refnamediv>
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<refname>intval</refname>
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<refpurpose>Get integer value of a variable</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>intval</function></funcdef>
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<paramdef>mixed <parameter>var</parameter></paramdef>
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<paramdef>int
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<parameter><optional>base</optional></parameter>
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</paramdef>
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</funcprototype>
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</funcsynopsis>
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<simpara>
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Returns the <type>integer</type> value of <parameter>var</parameter>,
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using the specified base for the conversion (the default is
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base 10).
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</simpara>
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<simpara>
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<parameter>var</parameter> may be any scalar type. You cannot use
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<function>intval</function> on <type>array</type>s or <type>object</type>s.
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</simpara>
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<note>
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<para>
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The <parameter>base</parameter> argument for
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<function>intval</function> has no effect unless the
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<parameter>var</parameter> argument is a string.
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</para>
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</note>
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<simpara>
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See also <function>floatval</function>,
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<function>strval</function>, <function>settype</function> and
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<link linkend="language.types.type-juggling">Type
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juggling</link>.
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</simpara>
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</refsect1>
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</refentry>
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<refentry id="function.is-array">
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<refnamediv>
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<refname>is_array</refname>
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<refpurpose>Finds whether a variable is an array</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>bool <function>is_array</function></funcdef>
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<paramdef>mixed <parameter>var</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<para>
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Returns &true; if <parameter>var</parameter> is an <type>array</type>, &false;
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otherwise.
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</para>
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<para>
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See also
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<function>is_float</function>,
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<function>is_int</function>,
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<function>is_integer</function>,
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<function>is_string</function>, and
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<function>is_object</function>.
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</para>
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</refsect1>
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</refentry>
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<refentry id="function.is-bool">
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<refnamediv>
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<refname>is_bool</refname>
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<refpurpose>
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Finds out whether a variable is a boolean
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</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>bool
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<function>is_bool</function>
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</funcdef>
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<paramdef>mixed
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<parameter>var</parameter>
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</paramdef>
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</funcprototype>
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</funcsynopsis>
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<para>
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Returns &true; if the <parameter>var</parameter> parameter is
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a <type>boolean</type>.
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</para>
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<para>
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See also
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<function>is_array</function>,
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<function>is_float</function>,
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<function>is_int</function>,
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<function>is_integer</function>,
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<function>is_string</function>, and
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<function>is_object</function>.
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</para>
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</refsect1>
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</refentry>
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<refentry id="function.is-double">
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<refnamediv>
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<refname>is_double</refname>
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<refpurpose>Alias of <function>is_float</function></refpurpose>
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</refnamediv>
|
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<refsect1>
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<title>Description</title>
|
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<para>
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This function is an alias of <function>is_float</function>.
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</para>
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</refsect1>
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</refentry>
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<refentry id="function.is-float">
|
|
<refnamediv>
|
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<refname>is_float</refname>
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<refpurpose>Finds whether a variable is a float</refpurpose>
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</refnamediv>
|
|
<refsect1>
|
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<title>Description</title>
|
|
<funcsynopsis>
|
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<funcprototype>
|
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<funcdef>bool <function>is_float</function></funcdef>
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<paramdef>mixed <parameter>var</parameter></paramdef>
|
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</funcprototype>
|
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</funcsynopsis>
|
|
<simpara>
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Returns &true; if <parameter>var</parameter> is a <type>float</type>,
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&false; otherwise.
|
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</simpara>
|
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<simpara>
|
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See also
|
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<function>is_bool</function>,
|
|
<function>is_int</function>,
|
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<function>is_integer</function>,
|
|
<function>is_string</function>,
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<function>is_array</function>, and
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<function>is_object</function>,
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|
</simpara>
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|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-int">
|
|
<refnamediv>
|
|
<refname>is_int</refname>
|
|
<refpurpose>Find whether a variable is an integer</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool <function>is_int</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
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Returns &true; if <parameter>var</parameter> is an <type>integer</type>
|
|
&false; otherwise.
|
|
</simpara>
|
|
<simpara>
|
|
See also <function>is_bool</function>,
|
|
<function>is_float</function>,
|
|
<function>is_integer</function>,
|
|
<function>is_string</function>,
|
|
<function>is_array</function>, and
|
|
<function>is_object</function>.
|
|
</simpara>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-integer">
|
|
<refnamediv>
|
|
<refname>is_integer</refname>
|
|
<refpurpose>Alias of <function>is_int</function></refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<para>
|
|
This function is an alias of <function>is_int</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-long">
|
|
<refnamediv>
|
|
<refname>is_long</refname>
|
|
<refpurpose>Alias of <function>is_int</function></refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<para>
|
|
This function is an alias of <function>is_int</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-null">
|
|
<refnamediv>
|
|
<refname>is_null</refname>
|
|
<refpurpose>
|
|
Finds whether a variable is &null;
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool <function>is_null</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
Returns &true; if <parameter>var</parameter> is <type>null</type>,
|
|
&false; otherwise.
|
|
</para>
|
|
<para>
|
|
See also <function>is_bool</function>,
|
|
<function>is_numeric</function>,
|
|
<function>is_float</function>,
|
|
<function>is_int</function>,
|
|
<function>is_string</function>,
|
|
<function>is_object</function>,
|
|
<function>is_array</function>, and
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
|
|
<refentry id="function.is-numeric">
|
|
<refnamediv>
|
|
<refname>is_numeric</refname>
|
|
<refpurpose>
|
|
Finds whether a variable is a number or a numeric string
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool <function>is_numeric</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
Returns &true; if <parameter>var</parameter> is a number or a
|
|
numeric string, &false; otherwise.
|
|
</para>
|
|
<para>
|
|
See also <function>is_bool</function>,
|
|
<function>is_float</function>,
|
|
<function>is_int</function>,
|
|
<function>is_string</function>,
|
|
<function>is_object</function>,
|
|
<function>is_array</function>, and
|
|
<function>is_integer</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-object">
|
|
<refnamediv>
|
|
<refname>is_object</refname>
|
|
<refpurpose>Finds whether a variable is an object</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool <function>is_object</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
Returns &true; if <parameter>var</parameter> is an <type>object</type>,
|
|
&false; otherwise.
|
|
</para>
|
|
<para>
|
|
See also <function>is_bool</function>,
|
|
<function>is_int</function>,
|
|
<function>is_integer</function>,
|
|
<function>is_float</function>,
|
|
<function>is_string</function>, and
|
|
<function>is_array</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-real">
|
|
<refnamediv>
|
|
<refname>is_real</refname>
|
|
<refpurpose>Alias of <function>is_float</function></refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<para>
|
|
This function is an alias of <function>is_float</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-resource">
|
|
<refnamediv>
|
|
<refname>is_resource</refname>
|
|
<refpurpose>
|
|
Finds whether a variable is a resource
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool
|
|
<function>is_resource</function>
|
|
</funcdef>
|
|
<paramdef>mixed
|
|
<parameter>var</parameter>
|
|
</paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
<function>is_resource</function> returns &true; if the variable
|
|
given by the <parameter>var</parameter> parameter is a
|
|
<type>resource</type>, otherwise it returns &false;.
|
|
</para>
|
|
<para>
|
|
See the documentation on the <type>resource</type>-type for
|
|
more information.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.is-scalar">
|
|
<refnamediv>
|
|
<refname>is_scalar</refname>
|
|
<refpurpose>
|
|
Finds whether a variable is a scalar
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool
|
|
<function>is_scalar</function>
|
|
</funcdef>
|
|
<paramdef>mixed
|
|
<parameter>var</parameter>
|
|
</paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
<function>is_scalar</function> returns &true; if the variable
|
|
given by the <parameter>var</parameter> parameter is a scalar,
|
|
otherwise it returns &false;.
|
|
</para>
|
|
<para>
|
|
Scalar variables are those containing an <type>integer</type>,
|
|
<type>float</type>, <type>string</type> or <type>boolean</type>.
|
|
For example:
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
<!-- TODO: better example, this one can be quite misleading for unexperienced
|
|
programmers -->
|
|
function show_var($var) {
|
|
if (is_scalar($var))
|
|
echo $var;
|
|
else
|
|
var_dump($var);
|
|
}
|
|
|
|
$pi = 3.1416;
|
|
$proteins = array("hemoglobin", "cytochrome c oxidase", "ferredoxin");
|
|
|
|
show_var($pi);
|
|
// prints: 3.1416
|
|
|
|
show_var($proteins)
|
|
// prints:
|
|
// array(3) {
|
|
// [0]=>
|
|
// string(10) "hemoglobin"
|
|
// [1]=>
|
|
// string(20) "cytochrome c oxidase"
|
|
// [2]=>
|
|
// string(10) "ferredoxin"
|
|
// }
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<note>
|
|
<para>
|
|
<function>is_scalar</function> does not consider <type>resource</type>
|
|
type values to be scalar values. This behavior is intentional:
|
|
Resources are abstract datatypes which are currently based on
|
|
integers. This implementation detail should not be relied upon,
|
|
as it may change.
|
|
</para>
|
|
</note>
|
|
<note>
|
|
<para>
|
|
Since 4.0.5
|
|
</para>
|
|
</note>
|
|
<para>
|
|
See also <function>is_bool</function>,
|
|
<function>is_numeric</function>,
|
|
<function>is_float</function>,
|
|
<function>is_int</function>,
|
|
<function>is_real</function>,
|
|
<function>is_string</function>,
|
|
<function>is_object</function>,
|
|
<function>is_array</function>, and
|
|
<function>is_integer</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
|
|
<refentry id="function.is-string">
|
|
<refnamediv>
|
|
<refname>is_string</refname>
|
|
<refpurpose>Finds whether a variable is a string</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>bool <function>is_string</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
Returns &true; if <parameter>var</parameter> is a <type>string</type>,
|
|
&false; otherwise.
|
|
</para>
|
|
<para>
|
|
See also <function>is_bool</function>,
|
|
<function>is_int</function>,
|
|
<function>is_integer</function>,
|
|
<function>is_float</function>,
|
|
<function>is_real</function>,
|
|
<function>is_object</function>, and
|
|
<function>is_array</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.isset">
|
|
<refnamediv>
|
|
<refname>isset</refname>
|
|
<refpurpose>Determine whether a variable is set</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>boolean <function>isset</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
|
Returns &true; if <parameter>var</parameter>
|
|
exists; &false; otherwise.
|
|
</simpara>
|
|
<para>
|
|
If a variable has been unset with <function>unset</function>,
|
|
it will no longer be <function>isset</function>. <function>isset</function>
|
|
will return &false; if testing a variable that has been
|
|
set to &null;. Also note that a &null; byte (<literal>"\0"</literal>)
|
|
is not equivalent to the PHP &null; constant.
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
$a = "test";
|
|
echo isset ($a); // TRUE
|
|
|
|
unset ($a);
|
|
echo isset ($a); // FALSE
|
|
|
|
$foo = NULL;
|
|
print isset ($foo); // FALSE
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<simpara>
|
|
See also <function>empty</function> and
|
|
<function>unset</function>.
|
|
</simpara>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.print-r">
|
|
<refnamediv>
|
|
<refname>print_r</refname>
|
|
<refpurpose>
|
|
Prints human-readable information about a variable
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>void <function>print_r</function></funcdef>
|
|
<paramdef>mixed <parameter>expression</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
|
This function displays information about the values of variables
|
|
in a way that's readable by humans. If given a <type>string</type>,
|
|
<type>integer</type> or <type>float</type>, the value itself will be
|
|
printed. If given an <type>array</type>,
|
|
values will be presented in a format that shows keys and
|
|
elements. Similar notation is used for <type>object</type>s.
|
|
</simpara>
|
|
<simpara>
|
|
Remember that <function>print_r</function> will move the array
|
|
pointer to the end. Use <function>reset</function> to bring
|
|
it back to beginning.
|
|
</simpara>
|
|
&tip.ob-capture;
|
|
<simpara>
|
|
Compare <function>print_r</function> to
|
|
<function>var_dump</function>.
|
|
</simpara>
|
|
<para>
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
<?php
|
|
$a = array (1, 2, array ("a", "b", "c"));
|
|
print_r ($a);
|
|
?>
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<warning>
|
|
<para>
|
|
This function will continue forever if given an <type>array</type>
|
|
or <type>object</type>
|
|
that contains a direct or indirect reference to itself or that
|
|
contains an <type>array</type> or <type>object</type> on a deeper
|
|
level that does so.
|
|
This is especially &true; for <literal>print_r($GLOBALS)</literal>,
|
|
as <literal>$GLOBALS</literal> is itself a global variable and
|
|
contains a reference to itself as such.
|
|
</para>
|
|
</warning>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.serialize">
|
|
<refnamediv>
|
|
<refname>serialize</refname>
|
|
<refpurpose>
|
|
Generates a storable representation of a value
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>string <function>serialize</function></funcdef>
|
|
<paramdef>mixed <parameter>value</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
|
<function>serialize</function> returns a string containing a
|
|
byte-stream representation of <parameter>value</parameter> that
|
|
can be stored anywhere.
|
|
</simpara>
|
|
<simpara>
|
|
This is useful for storing or passing PHP values around without
|
|
losing their type and structure.
|
|
</simpara>
|
|
<simpara>
|
|
To make the serialized string into a PHP value again, use
|
|
<function>unserialize</function>. <function>serialize</function>
|
|
handles all types, except the <type>resource</type>-type.
|
|
You can even <function>serialize</function> arrays that contain
|
|
references to itself. References inside the array/object you
|
|
are <function>serialize</function>ing will also be stored.
|
|
</simpara>
|
|
<!-- TODO
|
|
in 4.0.4pl1 this didn't work properly, however, there
|
|
been some fixes. I don't know whether this all
|
|
works correctly now, and if so, whether it is since 405
|
|
or 406
|
|
<note>
|
|
<simpara>
|
|
This didn't work correctly until 4.0.?
|
|
</simpara>
|
|
</note>
|
|
</simpara>
|
|
-->
|
|
<note>
|
|
<para>
|
|
In PHP 3, object properties will be serialized, but methods are
|
|
lost. PHP 4 removes that limitation and restores both properties
|
|
and methods. Please see the <link
|
|
linkend="language.oop.serialization">Serializing Objects</link>
|
|
section of <link linkend="language.oop">Classes and
|
|
Objects</link> for more information.
|
|
</para>
|
|
</note>
|
|
<para>
|
|
<example>
|
|
<title><function>serialize</function> example</title>
|
|
<programlisting role="php">
|
|
// $session_data contains a multi-dimensional array with session
|
|
// information for the current user. We use serialize() to store
|
|
// it in a database at the end of the request.
|
|
|
|
$conn = odbc_connect ("webdb", "php", "chicken");
|
|
$stmt = odbc_prepare ($conn,
|
|
"UPDATE sessions SET data = ? WHERE id = ?");
|
|
$sqldata = array (serialize($session_data), $PHP_AUTH_USER);
|
|
if (!odbc_execute ($stmt, &$sqldata)) {
|
|
$stmt = odbc_prepare($conn,
|
|
"INSERT INTO sessions (id, data) VALUES(?, ?)");
|
|
if (!odbc_execute($stmt, &$sqldata)) {
|
|
/* Something went wrong. Bitch, whine and moan. */
|
|
}
|
|
}
|
|
</programlisting>
|
|
</example>
|
|
</para>
|
|
<para>
|
|
See Also: <function>unserialize</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.settype">
|
|
<refnamediv>
|
|
<refname>settype</refname>
|
|
<refpurpose>Set the type of a variable</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>boolean <function>settype</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
<paramdef>string <parameter>type</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
Set the type of variable <parameter>var</parameter> to
|
|
<parameter>type</parameter>.
|
|
</para>
|
|
<para>
|
|
Possibles values of <parameter>type</parameter> are:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<simpara>
|
|
"boolean" (or, since PHP 4.2.0, "bool")
|
|
</simpara>
|
|
</listitem>
|
|
<listitem>
|
|
<simpara>
|
|
"integer" (or, since PHP 4.2.0, "int")
|
|
</simpara>
|
|
</listitem>
|
|
<listitem>
|
|
<simpara>
|
|
"float" (only possible since PHP 4.2.0, for older versions use the
|
|
deprecated variant "double")
|
|
</simpara>
|
|
</listitem>
|
|
<listitem>
|
|
<simpara>
|
|
"string"
|
|
</simpara>
|
|
</listitem>
|
|
<listitem>
|
|
<simpara>
|
|
"array"
|
|
</simpara>
|
|
</listitem>
|
|
<listitem>
|
|
<simpara>
|
|
"object"
|
|
</simpara>
|
|
</listitem>
|
|
<listitem>
|
|
<simpara>
|
|
"null" (since PHP 4.0.8)
|
|
</simpara>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
<para>
|
|
Returns &true; if successful; otherwise returns
|
|
&false;.
|
|
</para>
|
|
<para>
|
|
<example>
|
|
<title><function>settype</function> example</title>
|
|
<programlisting role="php">
|
|
$foo = "5bar"; // string
|
|
$bar = true; // boolean
|
|
|
|
settype($foo, "integer"); // $foo is now 5 (integer)
|
|
settype($bar, "string"); // $bar is now "1" (string)
|
|
</programlisting>
|
|
</example>
|
|
</para>
|
|
<para>
|
|
See also <function>gettype</function>,
|
|
<link linkend="language.types.typecasting">type-casting</link> and
|
|
<link linkend="language.types.type-juggling">type-juggling</link>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.strval">
|
|
<refnamediv>
|
|
<refname>strval</refname>
|
|
<refpurpose>Get string value of a variable</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>string <function>strval</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
|
Returns the <type>string</type> value of <parameter>var</parameter>.
|
|
See the documentation on <type>string</type> for more information
|
|
on converting to string.
|
|
</simpara>
|
|
<simpara>
|
|
<parameter>var</parameter> may be any scalar type. You cannot use
|
|
<function>strval</function> on arrays or objects.
|
|
</simpara>
|
|
<simpara>
|
|
See also <function>floatval</function>,
|
|
<function>intval</function>, <function>settype</function> and
|
|
<link linkend="language.types.type-juggling">Type
|
|
juggling</link>.
|
|
</simpara>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.unserialize">
|
|
<refnamediv>
|
|
<refname>unserialize</refname>
|
|
<refpurpose>
|
|
Creates a PHP value from a stored representation
|
|
</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>mixed <function>unserialize</function></funcdef>
|
|
<paramdef>string <parameter>str</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
|
<function>unserialize</function> takes a single serialized
|
|
variable (see <function>serialize</function>) and converts it
|
|
back into a PHP value. The converted value is returned, and can
|
|
be an <type>integer</type>, <type>float</type>,
|
|
<type>string</type>, <type>array</type> or <type>object</type>.
|
|
If an object was serialized, its methods are not preserved in the
|
|
returned value.
|
|
</simpara>
|
|
<note>
|
|
<para>
|
|
In PHP 3, methods are not preserved when unserializing a
|
|
serialized object. PHP 4 removes that limitation and restores
|
|
both properties and methods. Please see the <link
|
|
linkend="language.oop.serialization">Serializing Objects</link>
|
|
section of <link linkend="language.oop">Classes and
|
|
Objects</link> or more information.
|
|
</para>
|
|
</note>
|
|
<para>
|
|
<example>
|
|
<title><function>unserialize</function> example</title>
|
|
<programlisting role="php">
|
|
// Here, we use unserialize() to load session data from a database
|
|
// into $session_data. This example complements the one described
|
|
// with <function>serialize</function>.
|
|
|
|
$conn = odbc_connect ("webdb", "php", "chicken");
|
|
$stmt = odbc_prepare ($conn, "SELECT data FROM sessions WHERE id = ?");
|
|
$sqldata = array ($PHP_AUTH_USER);
|
|
if (!odbc_execute ($stmt, &$sqldata) || !odbc_fetch_into ($stmt, &$tmp)) {
|
|
// if the execute or fetch fails, initialize to empty array
|
|
$session_data = array();
|
|
} else {
|
|
// we should now have the serialized data in $tmp[0].
|
|
$session_data = unserialize ($tmp[0]);
|
|
if (!is_array ($session_data)) {
|
|
// something went wrong, initialize to empty array
|
|
$session_data = array();
|
|
}
|
|
}
|
|
</programlisting>
|
|
</example>
|
|
</para>
|
|
<para>
|
|
See Also: <function>serialize</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.unset">
|
|
<refnamediv>
|
|
<refname>unset</refname>
|
|
<refpurpose>Unset a given variable</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>void <function>unset</function></funcdef>
|
|
<paramdef>mixed <parameter>var</parameter></paramdef>
|
|
<paramdef>mixed <parameter><optional>var</optional></parameter></paramdef>
|
|
<paramdef><parameter><optional>...</optional></parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<para>
|
|
<function>unset</function> destroys the specified variables. Note
|
|
that in PHP 3, <function>unset</function> will always return &true;
|
|
(actually, the integer value 1). In PHP 4, however,
|
|
<function>unset</function> is no longer a &true; function: it is
|
|
now a statement. As such no value is returned, and attempting to
|
|
take the value of <function>unset</function> results in a parse
|
|
error.
|
|
</para>
|
|
<para>
|
|
<example>
|
|
<title><function>unset</function> example</title>
|
|
<programlisting role="php">
|
|
// destroy a single variable
|
|
unset ($foo);
|
|
|
|
// destroy a single element of an array
|
|
unset ($bar['quux']);
|
|
|
|
// destroy more than one variable
|
|
unset ($foo1, $foo2, $foo3);
|
|
</programlisting>
|
|
</example>
|
|
</para>
|
|
<para>
|
|
The behavior of <function>unset</function> inside of a function
|
|
can vary depending on what type of variable you are attempting to
|
|
destroy.
|
|
</para>
|
|
<para>
|
|
If a globalized variable is <function>unset</function> inside of
|
|
a function, only the local variable is destroyed. The variable
|
|
in the calling environment will retain the same value as before
|
|
<function>unset</function> was called.
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
function destroy_foo() {
|
|
global $foo;
|
|
unset($foo);
|
|
}
|
|
|
|
$foo = 'bar';
|
|
destroy_foo();
|
|
echo $foo;
|
|
</programlisting>
|
|
</informalexample>
|
|
The above example would output:
|
|
<informalexample>
|
|
<programlisting>
|
|
bar
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<para>
|
|
If a variable that is PASSED BY REFERENCE is
|
|
<function>unset</function> inside of a function, only the local
|
|
variable is destroyed. The variable in the calling environment
|
|
will retain the same value as before <function>unset</function>
|
|
was called.
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
function foo(&$bar) {
|
|
unset($bar);
|
|
$bar = "blah";
|
|
}
|
|
|
|
$bar = 'something';
|
|
echo "$bar\n";
|
|
|
|
foo($bar);
|
|
echo "$bar\n";
|
|
</programlisting>
|
|
</informalexample>
|
|
The above example would output:
|
|
<informalexample>
|
|
<programlisting>
|
|
something
|
|
something
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<para>
|
|
If a static variable is <function>unset</function> inside of a
|
|
function, <function>unset</function> unsets the reference to the
|
|
static variable, rather than the static variable itself.
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
function foo() {
|
|
static $a;
|
|
$a++;
|
|
echo "$a\n";
|
|
|
|
unset($a);
|
|
}
|
|
|
|
foo();
|
|
foo();
|
|
foo();
|
|
</programlisting>
|
|
</informalexample>
|
|
The above example would output:
|
|
<informalexample>
|
|
<programlisting>
|
|
1
|
|
2
|
|
3
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<para>
|
|
If you would like to <function>unset</function> a global variable inside of a function, you can use the <parameter>$GLOBALS</parameter> array to do so:
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
function foo() {
|
|
unset($GLOBALS['bar']);
|
|
}
|
|
|
|
$bar = "something";
|
|
foo();
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<note>
|
|
<para>
|
|
<function>unset</function> is a language construct.
|
|
</para>
|
|
</note>
|
|
<para>
|
|
See also <function>isset</function> and
|
|
<function>empty</function>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<refentry id="function.var-dump">
|
|
<refnamediv>
|
|
<refname>var_dump</refname>
|
|
<refpurpose>Dumps information about a variable</refpurpose>
|
|
</refnamediv>
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>void <function>var_dump</function></funcdef>
|
|
<paramdef>mixed <parameter>expression</parameter></paramdef>
|
|
<paramdef>mixed <parameter><optional>expression</optional></parameter></paramdef>
|
|
<paramdef><parameter><optional>...</optional></parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
<simpara>
|
|
This function returns structured information about one or more expressions
|
|
that includes its type and value. Arrays are explored
|
|
recursively with values indented to show structure.
|
|
</simpara>
|
|
&tip.ob-capture;
|
|
<simpara>
|
|
Compare <function>var_dump</function> to
|
|
<function>print_r</function>.
|
|
</simpara>
|
|
<para>
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
<pre>
|
|
<?php
|
|
$a = array (1, 2, array ("a", "b", "c"));
|
|
var_dump ($a);
|
|
|
|
/* output:
|
|
array(3) {
|
|
[0]=>
|
|
int(1)
|
|
[1]=>
|
|
int(2)
|
|
[2]=>
|
|
array(3) {
|
|
[0]=>
|
|
string(1) "a"
|
|
[1]=>
|
|
string(1) "b"
|
|
[2]=>
|
|
string(1) "c"
|
|
}
|
|
}
|
|
|
|
*/
|
|
|
|
$b = 3.1; $c = TRUE;
|
|
var_dump($b,$c);
|
|
|
|
/* output:
|
|
float(3.1)
|
|
bool(true)
|
|
|
|
*/
|
|
?>
|
|
</pre>
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
</reference>
|
|
|
|
<!-- Keep this comment at the end of the file
|
|
Local variables:
|
|
mode: sgml
|
|
sgml-omittag:t
|
|
sgml-shorttag:t
|
|
sgml-minimize-attributes:nil
|
|
sgml-always-quote-attributes:t
|
|
sgml-indent-step:1
|
|
sgml-indent-data:t
|
|
sgml-parent-document:nil
|
|
sgml-default-dtd-file:"../../manual.ced"
|
|
sgml-exposed-tags:nil
|
|
sgml-local-catalogs:nil
|
|
sgml-local-ecat-files:nil
|
|
End:
|
|
vim600: syn=xml fen fdm=syntax fdl=2 si
|
|
vim: et tw=78 syn=sgml
|
|
vi: ts=1 sw=1
|
|
-->
|