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<refentry id="function.ereg-replace">
 <refnamediv>
  <refname>ereg_replace</refname>
  <refpurpose>Replace regular expression</refpurpose>
 </refnamediv>
 <refsect1>
  <title>Description</title>
  <methodsynopsis>
   <type>string</type><methodname>ereg_replace</methodname>
   <methodparam><type>string</type><parameter>pattern</parameter></methodparam>
   <methodparam><type>string</type><parameter>replacement</parameter></methodparam>
   <methodparam><type>string</type><parameter>string</parameter></methodparam>
  </methodsynopsis>
  <simpara>
   This function scans <parameter>string</parameter> for matches to
   <parameter>pattern</parameter>, then replaces the matched text
   with <parameter>replacement</parameter>.
  </simpara>
  <simpara>
   The modified string is returned. (Which may mean that the
   original string is returned if there are no matches to be
   replaced.)
  </simpara>
  <simpara>
   If <parameter>pattern</parameter> contains parenthesized
   substrings, <parameter>replacement</parameter> may contain
   substrings of the form
   <literal>\\<replaceable>digit</replaceable></literal>, which will
   be replaced by the text matching the digit'th parenthesized
   substring; <literal>\\0</literal> will produce the entire
   contents of string.  Up to nine substrings may be used.
   Parentheses may be nested, in which case they are counted by the
   opening parenthesis.
  </simpara>
  <simpara>
   If no matches are found in <parameter>string</parameter>, then
   <parameter>string</parameter> will be returned unchanged.
  </simpara>
  <para>
   For example, the following code snippet prints "This was a test"
   three times:
  </para>
  <para>
   <example>
    <title><function>ereg_replace</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php

$string = "This is a test";
echo str_replace(" is", " was", $string);
echo ereg_replace("( )is", "\\1was", $string);
echo ereg_replace("(( )is)", "\\2was", $string);

?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   One thing to take note of is that if you use an integer value as
   the <parameter>replacement</parameter> parameter, you may not get
   the results you expect. This is because
   <function>ereg_replace</function> will interpret the number as
   the ordinal value of a character, and apply that. For instance:
  </para>
  <para>
   <example>
    <title><function>ereg_replace</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
/* This will not work as expected. */
$num = 4;
$string = "This string has four words.";
$string = ereg_replace('four', $num, $string);
echo $string;   /* Output: 'This string has   words.' */

/* This will work. */
$num = '4';
$string = "This string has four words.";
$string = ereg_replace('four', $num, $string);
echo $string;   /* Output: 'This string has 4 words.' */
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title>Replace URLs with links</title>
    <programlisting role="php">
<![CDATA[
<?php
$text = ereg_replace("[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]",
                     "<a href=\"\\0\">\\0</a>", $text);
?>
]]>
    </programlisting>
   </example>
  </para>
  <tip>
   <para>
    <function>preg_replace</function>, which uses a Perl-compatible
    regular expression syntax, is often a faster alternative to
    <function>ereg_replace</function>.
   </para>
  </tip>
  <para>
   See also <function>ereg</function>, <function>eregi</function>,
   <function>eregi_replace</function>, <function>str_replace</function>, and
   <function>preg_match</function>.
  </para>
 </refsect1>
</refentry>
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