mirror of
https://github.com/sigmasternchen/php-doc-en
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1b6cf34f23
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@292327 c90b9560-bf6c-de11-be94-00142212c4b1
383 lines
11 KiB
XML
383 lines
11 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision$ -->
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<refentry xml:id="function.preg-replace" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>preg_replace</refname>
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<refpurpose>Perform a regular expression search and replace</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>preg_replace</methodname>
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<methodparam><type>mixed</type><parameter>pattern</parameter></methodparam>
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<methodparam><type>mixed</type><parameter>replacement</parameter></methodparam>
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<methodparam><type>mixed</type><parameter>subject</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>limit</parameter><initializer>-1</initializer></methodparam>
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<methodparam choice="opt"><type>int</type><parameter role="reference">count</parameter></methodparam>
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</methodsynopsis>
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<para>
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Searches <parameter>subject</parameter> for matches to
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<parameter>pattern</parameter> and replaces them with
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<parameter>replacement</parameter>.
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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>pattern</parameter></term>
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<listitem>
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<para>
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The pattern to search for. It can be either a string or an array with
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strings.
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</para>
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<para>
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The <literal>e</literal> modifier makes <function>preg_replace</function>
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treat the <parameter>replacement</parameter> parameter as PHP code after
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the appropriate references substitution is done. Tip: make sure that
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<parameter>replacement</parameter> constitutes a valid PHP code string,
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otherwise PHP will complain about a parse error at the line containing
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<function>preg_replace</function>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>replacement</parameter></term>
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<listitem>
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<para>
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The string or an array with strings to replace. If this parameter is a
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string and the <parameter>pattern</parameter> parameter is an array,
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all patterns will be replaced by that string. If both
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<parameter>pattern</parameter> and <parameter>replacement</parameter>
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parameters are arrays, each <parameter>pattern</parameter> will be
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replaced by the <parameter>replacement</parameter> counterpart. If
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there are fewer elements in the <parameter>replacement</parameter>
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array than in the <parameter>pattern</parameter> array, any extra
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<parameter>pattern</parameter>s will be replaced by an empty string.
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</para>
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<para>
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<parameter>replacement</parameter> may contain references of the form
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<literal>\\<replaceable>n</replaceable></literal> or (since PHP 4.0.4)
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<literal>$<replaceable>n</replaceable></literal>, with the latter form
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being the preferred one. Every such reference will be replaced by the text
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captured by the <replaceable>n</replaceable>'th parenthesized pattern.
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<replaceable>n</replaceable> can be from 0 to 99, and
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<literal>\\0</literal> or <literal>$0</literal> refers to the text matched
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by the whole pattern. Opening parentheses are counted from left to right
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(starting from 1) to obtain the number of the capturing subpattern.
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To use backslash in replacement, it must be doubled
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(<literal>"\\\\"</literal> PHP string).
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</para>
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<para>
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When working with a replacement pattern where a backreference is
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immediately followed by another number (i.e.: placing a literal number
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immediately after a matched pattern), you cannot use the familiar
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<literal>\\1</literal> notation for your backreference.
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<literal>\\11</literal>, for example, would confuse
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<function>preg_replace</function> since it does not know whether you
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want the <literal>\\1</literal> backreference followed by a literal
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<literal>1</literal>, or the <literal>\\11</literal> backreference
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followed by nothing. In this case the solution is to use
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<literal>\${1}1</literal>. This creates an isolated
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<literal>$1</literal> backreference, leaving the <literal>1</literal>
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as a literal.
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</para>
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<para>
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When using the <literal>e</literal> modifier, this function escapes
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some characters (namely <literal>'</literal>, <literal>"</literal>,
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<literal>\</literal> and NULL) in the strings that replace the
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backreferences. This is done to ensure that no syntax errors arise
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from backreference usage with either single or double quotes (e.g.
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<literal>'strlen(\'$1\')+strlen("$2")'</literal>). Make sure you are
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aware of PHP's <link linkend="language.types.string">string
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syntax</link> to know exactly how the interpreted string will look
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like.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>subject</parameter></term>
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<listitem>
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<para>
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The string or an array with strings to search and replace.
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</para>
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<para>
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If <parameter>subject</parameter> is an array, then the search and
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replace is performed on every entry of <parameter>subject</parameter>,
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and the return value is an array as well.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>limit</parameter></term>
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<listitem>
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<para>
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The maximum possible replacements for each pattern in each
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<parameter>subject</parameter> string. Defaults to
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<literal>-1</literal> (no limit).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>count</parameter></term>
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<listitem>
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<para>
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If specified, this variable will be filled with the number of
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replacements done.
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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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<function>preg_replace</function> returns an array if the
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<parameter>subject</parameter> parameter is an array, or a string
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otherwise.
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</para>
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<para>
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If matches are found, the new <parameter>subject</parameter> will
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be returned, otherwise <parameter>subject</parameter> will be
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returned unchanged or &null; if an error occurred.
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</para>
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</refsect1>
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<refsect1 role="changelog">
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&reftitle.changelog;
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<para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>5.1.0</entry>
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<entry>
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Added the <parameter>count</parameter> parameter
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</entry>
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</row>
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<row>
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<entry>4.0.4</entry>
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<entry>
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Added the '$n' form for the <parameter>replacement</parameter> parameter
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</entry>
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</row>
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<row>
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<entry>4.0.2</entry>
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<entry>
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Added the <parameter>limit</parameter> parameter
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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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>Using backreferences followed by numeric literals</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$string = 'April 15, 2003';
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$pattern = '/(\w+) (\d+), (\d+)/i';
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$replacement = '${1}1,$3';
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echo preg_replace($pattern, $replacement, $string);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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April1,2003
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title>Using indexed arrays with <function>preg_replace</function></title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$string = 'The quick brown fox jumped over the lazy dog.';
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$patterns = array();
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$patterns[0] = '/quick/';
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$patterns[1] = '/brown/';
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$patterns[2] = '/fox/';
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$replacements = array();
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$replacements[2] = 'bear';
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$replacements[1] = 'black';
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$replacements[0] = 'slow';
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echo preg_replace($patterns, $replacements, $string);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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The bear black slow jumped over the lazy dog.
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]]>
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</screen>
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<para>
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By ksorting patterns and replacements, we should get what we wanted.
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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ksort($patterns);
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ksort($replacements);
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echo preg_replace($patterns, $replacements, $string);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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The slow black bear jumped over the lazy dog.
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title>Replacing several values</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$patterns = array ('/(19|20)(\d{2})-(\d{1,2})-(\d{1,2})/',
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'/^\s*{(\w+)}\s*=/');
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$replace = array ('\3/\4/\1\2', '$\1 =');
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echo preg_replace($patterns, $replace, '{startDate} = 1999-5-27');
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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$startDate = 5/27/1999
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title>Using the 'e' modifier</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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preg_replace("/(<\/?)(\w+)([^>]*>)/e",
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"'\\1'.strtoupper('\\2').'\\3'",
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$html_body);
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?>
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]]>
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</programlisting>
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<para>
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This would capitalize all HTML tags in the input text.
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</para>
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</example>
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</para>
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<para>
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<example>
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<title>Strip whitespace</title>
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<para>
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This example strips excess whitespace from a string.
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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$str = 'foo o';
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$str = preg_replace('/\s\s+/', ' ', $str);
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// This will be 'foo o' now
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echo $str;
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?>
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]]>
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</programlisting>
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</example>
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</para>
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<para>
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<example>
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<title>Using the <parameter>count</parameter> parameter</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$count = 0;
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echo preg_replace(array('/\d/', '/\s/'), '*', 'xp 4 to', -1 , $count);
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echo $count; //3
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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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xp***to
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3
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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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<note>
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<para>
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When using arrays with <parameter>pattern</parameter> and
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<parameter>replacement</parameter>, the keys are processed in the order
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they appear in the array. This is <emphasis>not necessarily</emphasis> the
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same as the numerical index order. If you use indexes to identify which
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<parameter>pattern</parameter> should be replaced by which
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<parameter>replacement</parameter>, you should perform a
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<function>ksort</function> on each array prior to calling
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<function>preg_replace</function>.
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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>preg_filter</function></member>
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<member><function>preg_match</function></member>
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<member><function>preg_replace_callback</function></member>
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<member><function>preg_split</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:"~/.phpdoc/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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