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https://github.com/sigmasternchen/php-doc-en
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cd03365a66
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@231543 c90b9560-bf6c-de11-be94-00142212c4b1
140 lines
3.7 KiB
XML
140 lines
3.7 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.20 $ -->
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<refentry id="function.eval">
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<refnamediv>
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<refname>eval</refname>
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<refpurpose>Evaluate a string as PHP code</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type>mixed</type><methodname>eval</methodname>
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<methodparam><type>string</type><parameter>code_str</parameter></methodparam>
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</methodsynopsis>
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<para>
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Evaluates the string given in <parameter>code_str</parameter> as PHP code.
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Among other things, this can be useful for storing code in a database text
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field for later execution.
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</para>
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<para>
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There are some factors to keep in mind when using
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<function>eval</function>. Remember that the string passed must be valid
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PHP code, including things like terminating statements with a semicolon so
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the parser doesn't die on the line after the <function>eval</function>,
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and properly escaping things in <parameter>code_str</parameter>. To mix
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HTML output and PHP code you can use a closing PHP tag to leave PHP mode.
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</para>
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<para>
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Also remember that variables given values under <function>eval</function>
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will retain these values in the main script afterwards.
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</para>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>code_str</parameter></term>
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<listitem>
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<para>
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The code string to be evaluated.
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<parameter>code_str</parameter> does not have to contain <link
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linkend="language.basic-syntax.phpmode">PHP Opening tags</link>.
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</para>
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<para>
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A <literal>return</literal> statement will immediately terminate the
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evaluation of the string .
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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As of PHP 4, <function>eval</function> returns &null; unless
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<literal>return</literal> is called in the evaluated code, in which case
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the value passed to <literal>return</literal> is returned. In case of a
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parse error in the evaluated code, <function>eval</function> returns
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&false;.
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</para>
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<para>
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In PHP 3, <function>eval</function> does not return a value.
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</para>
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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example>
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<title><function>eval</function> example - simple text merge</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$string = 'cup';
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$name = 'coffee';
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$str = 'This is a $string with my $name in it.';
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echo $str. "\n";
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eval("\$str = \"$str\";");
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echo $str. "\n";
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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This is a $string with my $name in it.
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This is a cup with my coffee in it.
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]]>
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</screen>
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</example>
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</para>
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</refsect1>
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<refsect1 role="notes">
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&reftitle.notes;
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¬e.language-construct;
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&tip.ob-capture;
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<note>
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<para>
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In case of a fatal error in the evaluated code, the whole script exits.
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</para>
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</note>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>call_user_func</function></member>
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</simplelist>
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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