mirror of
https://github.com/sigmasternchen/php-doc-en
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d3992aa101
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@241386 c90b9560-bf6c-de11-be94-00142212c4b1
315 lines
8.3 KiB
XML
315 lines
8.3 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.26 $ -->
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<refentry xml:id="function.preg-match" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>preg_match</refname>
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<refpurpose>Perform a regular expression match</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>int</type><methodname>preg_match</methodname>
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<methodparam><type>string</type><parameter>pattern</parameter></methodparam>
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<methodparam><type>string</type><parameter>subject</parameter></methodparam>
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<methodparam choice="opt"><type>array</type><parameter role="reference">matches</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>flags</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>offset</parameter></methodparam>
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</methodsynopsis>
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<para>
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Searches <parameter>subject</parameter> for a match to the regular
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expression given in <parameter>pattern</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, as a string.
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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 input string.
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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>matches</parameter></term>
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<listitem>
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<para>
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If <parameter>matches</parameter> is provided, then it is filled with
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the results of search. <varname>$matches[0]</varname> will contain the
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text that matched the full pattern, <varname>$matches[1]</varname>
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will have the text that matched the first captured parenthesized
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subpattern, and so on.
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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>flags</parameter></term>
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<listitem>
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<para>
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<parameter>flags</parameter> can be the following flag:
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<variablelist>
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<varlistentry>
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<term><constant>PREG_OFFSET_CAPTURE</constant></term>
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<listitem>
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<simpara>
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If this flag is passed, for every occurring match the appendant string
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offset will also be returned. Note that this changes the return value
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in an array where every element is an array consisting of the matched
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string at index <literal>0</literal> and its string offset into
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<parameter>subject</parameter> at index <literal>1</literal>.
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</simpara>
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</listitem>
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</varlistentry>
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</variablelist>
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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>offset</parameter></term>
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<listitem>
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<para>
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Normally, the search starts from the beginning of the subject string.
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The optional parameter <parameter>offset</parameter> can be used to
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specify the alternate place from which to start the search (in bytes).
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</para>
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<note>
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<para>
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Using <parameter>offset</parameter> is not equivalent to passing
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<literal>substr($subject, $offset)</literal> to
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<function>preg_match</function> in place of the subject string,
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because <parameter>pattern</parameter> can contain assertions such as
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<emphasis>^</emphasis>, <emphasis>$</emphasis> or
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<emphasis>(?<=x)</emphasis>. Compare:
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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<?php
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$subject = "abcdef";
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$pattern = '/^def/';
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preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 3);
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print_r($matches);
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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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Array
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(
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)
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]]>
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</screen>
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<para>
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while this example
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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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$subject = "abcdef";
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$pattern = '/^def/';
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preg_match($pattern, substr($subject,3), $matches, PREG_OFFSET_CAPTURE);
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print_r($matches);
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?>
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]]>
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</programlisting>
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<para>
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will produce
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</para>
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<screen>
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<![CDATA[
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Array
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(
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[0] => Array
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(
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[0] => def
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[1] => 0
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)
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)
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]]>
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</screen>
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</informalexample>
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</para>
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</note>
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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_match</function> returns the number of times
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<parameter>pattern</parameter> matches. That will be either 0 times
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(no match) or 1 time because <function>preg_match</function> will stop
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searching after the first match. <function>preg_match_all</function>
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on the contrary will continue until it reaches the end of
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<parameter>subject</parameter>.
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<function>preg_match</function> returns &false; 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>4.3.3</entry>
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<entry>
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The <parameter>offset</parameter> parameter was added
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</entry>
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</row>
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<row>
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<entry>4.3.0</entry>
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<entry>
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The <constant>PREG_OFFSET_CAPTURE</constant> flag was added
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</entry>
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</row>
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<row>
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<entry>4.3.0</entry>
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<entry>
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The <parameter>flags</parameter> parameter was added
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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>Find the string of text "php"</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// The "i" after the pattern delimiter indicates a case-insensitive search
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if (preg_match("/php/i", "PHP is the web scripting language of choice.")) {
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echo "A match was found.";
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} else {
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echo "A match was not found.";
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}
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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>Find the word "web"</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* The \b in the pattern indicates a word boundary, so only the distinct
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* word "web" is matched, and not a word partial like "webbing" or "cobweb" */
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if (preg_match("/\bweb\b/i", "PHP is the web scripting language of choice.")) {
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echo "A match was found.";
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} else {
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echo "A match was not found.";
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}
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if (preg_match("/\bweb\b/i", "PHP is the website scripting language of choice.")) {
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echo "A match was found.";
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} else {
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echo "A match was not found.";
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}
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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>Getting the domain name out of a URL</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// get host name from URL
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preg_match('@^(?:http://)?([^/]+)@i',
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"http://www.php.net/index.html", $matches);
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$host = $matches[1];
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// get last two segments of host name
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preg_match('/[^.]+\.[^.]+$/', $host, $matches);
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echo "domain name is: {$matches[0]}\n";
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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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domain name is: php.net
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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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<tip>
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<para>
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Do not use <function>preg_match</function> if you only want to check if
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one string is contained in another string. Use
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<function>strpos</function> or <function>strstr</function> instead as
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they will be faster.
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</para>
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</tip>
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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_match_all</function></member>
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<member><function>preg_replace</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:"../../../../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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