mirror of
https://github.com/sigmasternchen/php-doc-en
synced 2025-03-20 02:48:56 +00:00
8ad0d94e1c
What's done: the migration guide itself, updates to existing functions and functionality, and new language features. What's not done: stub pages for new functions and methods. (I'd rather get this in now, though, than have it languish on my hard drive any longer so that other people can contribute.) What could use help: the generator chapter is pretty rough and ready. Better examples would be awesome. I certainly won't argue if somebody wants to add the function stubs, either. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@328430 c90b9560-bf6c-de11-be94-00142212c4b1
371 lines
11 KiB
XML
371 lines
11 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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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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Several <link linkend="reference.pcre.pattern.modifiers">PCRE modifiers</link>
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are also available, including '<literal>e</literal>' (PREG_REPLACE_EVAL), which
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is specific to this 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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</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>5.5.0</entry>
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<entry>
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The <literal>/e</literal> modifier is deprecated. Use
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<function>preg_replace_callback</function> instead.
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</entry>
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</row>
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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>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><link linkend="pcre.pattern">PCRE Patterns</link></member>
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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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<member><function>preg_last_error</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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