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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.25 $ -->
<refentry xml:id="function.eval" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>eval</refname>
<refpurpose>Evaluate a string as PHP code</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>mixed</type><methodname>eval</methodname>
<methodparam><type>string</type><parameter>code_str</parameter></methodparam>
</methodsynopsis>
<para>
Evaluates the string given in <parameter>code_str</parameter> as PHP code.
Among other things, this can be useful for storing code in a database text
field for later execution.
</para>
<para>
There are some factors to keep in mind when using
<function>eval</function>. Remember that the string passed must be valid
PHP code, including things like terminating statements with a semicolon so
the parser doesn't die on the line after the <function>eval</function>,
and properly escaping things in <parameter>code_str</parameter>. To mix
HTML output and PHP code you can use a closing PHP tag to leave PHP mode.
</para>
<para>
Also remember that variables given values under <function>eval</function>
will retain these values in the main script afterwards.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>code_str</parameter></term>
<listitem>
<para>
The code string to be evaluated.
<parameter>code_str</parameter> does not have to contain <link
linkend="language.basic-syntax.phpmode">PHP Opening tags</link>.
</para>
<para>
A <literal>return</literal> statement will immediately terminate the
evaluation of the string .
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
<function>eval</function> returns &null; unless
<literal>return</literal> is called in the evaluated code, in which case
the value passed to <literal>return</literal> is returned. If there is a
parse error in the evaluated code, <function>eval</function> returns
&false; and execution of the following code continues normally. It is
not possible to catch a parse error in <function>eval</function>
using <function>set_error_handler</function>.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>eval</function> example - simple text merge</title>
<programlisting role="php">
<![CDATA[
<?php
$string = 'cup';
$name = 'coffee';
$str = 'This is a $string with my $name in it.';
echo $str. "\n";
eval("\$str = \"$str\";");
echo $str. "\n";
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
This is a $string with my $name in it.
This is a cup with my coffee in it.
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
¬e.language-construct;
&tip.ob-capture;
<note>
<para>
In case of a fatal error in the evaluated code, the whole script exits.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>call_user_func</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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