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<refentry xml:id="function.preg-quote" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>preg_quote</refname>
  <refpurpose>Quote regular expression characters</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>preg_quote</methodname>
   <methodparam><type>string</type><parameter>str</parameter></methodparam>
   <methodparam choice="opt"><type class="union"><type>string</type><type>null</type></type><parameter>delimiter</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   <function>preg_quote</function> takes <parameter>str</parameter>
   and puts a backslash in front of every character that is part of
   the regular expression syntax.  This is useful if you have a
   run-time string that you need to match in some text and the
   string may contain special regex characters.
  </para>
  <para>
   The special regular expression characters are:
   <literal>. \ + * ? [ ^ ] $ ( ) { } = ! &lt; &gt; | : - #</literal>
  </para>
  <para>
   Note that <literal>/</literal> is not a special regular expression character.
  </para>
  <note>
   <para>
    Note that <function>preg_quote</function> is not meant to be applied to the
    $replacement string(s) of <function>preg_replace</function> etc.
   </para>
  </note>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>str</parameter></term>
     <listitem>
      <para>
       The input string.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>delimiter</parameter></term>
     <listitem>
      <para>
       If the optional <parameter>delimiter</parameter> is specified, it
       will also be escaped.  This is useful for escaping the delimiter
       that is required by the PCRE functions. The <literal>/</literal> is the most commonly
       used delimiter.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the quoted (escaped) string.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>7.3.0</entry>
       <entry>
        The <literal>#</literal> character is now quoted
       </entry>
      </row>
      <row>
       <entry>7.2.0</entry>
       <entry>
        <parameter>delimiter</parameter> is nullable now.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>preg_quote</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$keywords = '$40 for a g3/400';
$keywords = preg_quote($keywords, '/');
echo $keywords; // returns \$40 for a g3\/400
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title>Italicizing a word within some text</title>
    <programlisting role="php">
<![CDATA[
<?php
// In this example, preg_quote($word) is used to keep the
// asterisks from having special meaning to the regular
// expression.

$textbody = "This book is *very* difficult to find.";
$word = "*very*";
$textbody = preg_replace ("/" . preg_quote($word, '/') . "/",
                          "<i>" . $word . "</i>",
                          $textbody);
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  &note.bin-safe;
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><link linkend="pcre.pattern">PCRE Patterns</link></member>
    <member><function>escapeshellcmd</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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