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Update docs to be more informative on what's considered empty. And a few

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more see also's.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@128272 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Philip Olson 2003-05-21 20:42:06 +00:00
parent ca431331de
commit 9bff141792
1 changed files with 42 additions and 28 deletions
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70
reference/var/functions/empty.xml
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@ -1,10 +1,10 @@
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.4 $ -->
<!-- $Revision: 1.5 $ -->
<!-- splitted from ./en/functions/var.xml, last change in rev 1.2 -->
<refentry id="function.empty">
<refnamediv>
<refname>empty</refname>
<refpurpose>Determine whether a variable is set</refpurpose>
<refpurpose>Determine whether a variable is empty</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
@ -12,49 +12,63 @@
<type>bool</type><methodname>empty</methodname>
<methodparam><type>mixed</type><parameter>var</parameter></methodparam>
</methodsynopsis>
<note>
<para>
<function>empty</function> is a language construct.
</para>
</note>
&note.language-construct;
<para>
This is the opposite of
<function>empty</function> returns &false; if
<parameter>var</parameter> has a non-empty or non-zero value. In
otherwords, <literal>""</literal>, <literal>0</literal>,
<literal>"0"</literal>, &null;, &false;, <literal>array()</literal>,
<literal>var $var;</literal>, and objects with empty properties, are
all considered empty. &true; is returned if <parameter>var</parameter>
is not empty.
</para>
<para>
<function>empty</function> is the opposite of
<literal>(boolean) <parameter>var</parameter></literal>,
except that no warning is generated when the variable is not set.
See <link linkend="language.types.boolean.casting">converting
to boolean</link> for more information.
</para>
<!-- Returns &false; if <parameter>var</parameter> is set and has a
non-empty or non-zero value; &true; otherwise. -->
<informalexample>
<para>
<example>
<title>
A simple <function>empty</function> / <function>isset</function>
comparison.
</title>
<programlisting role="php">
<![CDATA[
<?php
$var = 0;
if (empty($var)) { // evaluates true
echo '$var is either 0 or not set at all';
// Evaluates to true because $var is empty
if (empty($var)) {
echo '$var is either 0, empty, or not set at all';
}
if (!isset($var)) { // evaluates false
echo '$var is not set at all';
// Evaluates as true because $var is set
if (isset($var)) {
echo '$var is set even though it is empty';
}
?>
]]>
</programlisting>
</informalexample>
</example>
</para>
&note.language-construct;
<note>
<para>
<function>empty</function> only checks variables as anything else will
result in a parse error. In otherwords, the following will not work:
<command>empty(addslashes($name))</command>.
</para>
</note>
<simpara>
Note that this is meaningless when used on anything which isn't a
variable; i.e. <command>empty (addslashes ($name))</command> has
no meaning since it would be checking whether something which
isn't a variable is a variable with a &false; value.
<!-- will even result in parse error (at least in PHP 4) -->
</simpara>
<simpara>
See also <function>isset</function> and
<function>unset</function>.
See also <function>isset</function>,
<function>unset</function>,
<function>array_key_exists</function>,
<function>count</function>, and
<function>strlen</function>.
</simpara>
</refsect1>
</refentry>