mirror of
https://github.com/sigmasternchen/php-doc-en
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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@147048 c90b9560-bf6c-de11-be94-00142212c4b1
286 lines
9.3 KiB
XML
286 lines
9.3 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.12 $ -->
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<!-- splitted from ./en/functions/pcre.xml, last change in rev 1.2 -->
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<refentry id="function.preg-replace">
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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>
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<title>Description</title>
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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></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>. If
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<parameter>limit</parameter> is specified, then only
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<parameter>limit</parameter> matches will be replaced; if
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<parameter>limit</parameter> is omitted or is -1, then all
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matches are replaced.
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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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</para>
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<para>
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When working with a replacement pattern where a backreference is immediately
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followed by another number (i.e.: placing a literal number immediately
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after a matched pattern), you cannot use the familiar <literal>\\1</literal>
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notation for your backreference. <literal>\\11</literal>, for example,
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would confuse <function>preg_replace</function> since it does not know whether
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you want the <literal>\\1</literal> backreference followed by a literal <literal>1</literal>,
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or the <literal>\\11</literal> backreference followed by nothing. In this case
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the solution is to use <literal>\${1}1</literal>. This creates an
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isolated <literal>$1</literal> backreference, leaving the <literal>1</literal>
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as a literal.
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</para>
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<para>
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<example>
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<title>Using backreferences followed by numeric literals</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$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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<para>
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This example will output :
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</para>
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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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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.
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</para>
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<para>
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Every parameter to <function>preg_replace</function> (except
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<parameter>limit</parameter>) can be an unidimensional array.
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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>
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the same as the numerical index order. If you use indexes to identify
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which <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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<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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$patterns[0] = "/quick/";
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$patterns[1] = "/brown/";
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$patterns[2] = "/fox/";
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$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, $string);
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?>
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]]>
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</programlisting>
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<para>
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Output:
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</para>
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<screen>
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<![CDATA[
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The bear black slow jumped over the lazy dog.
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]]>
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</screen>
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<para>
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By ksorting patterns and replacements, we should get what we wanted.
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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ksort($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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<para>
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Output :
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</para>
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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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If <parameter>subject</parameter> is an array, then the search
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and replace is performed on every entry of
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<parameter>subject</parameter>, and the return value is an array
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as well.
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</para>
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<para>
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If <parameter>pattern</parameter> and <parameter>replacement</parameter>
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are arrays, then <function>preg_replace</function> takes a value from
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each array and uses them to do search and replace on
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<parameter>subject</parameter>. If <parameter>replacement</parameter>
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has fewer values than <parameter>pattern</parameter>, then empty string
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is used for the rest of replacement values. If <parameter>pattern
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</parameter> is an array and <parameter>replacement</parameter> is a
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string, then this replacement string is used for every value of
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<parameter>pattern</parameter>. The converse would not make sense,
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though.
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</para>
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<para>
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<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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<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, $replace, "{startDate} = 1999-5-27");
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?>
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]]>
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</programlisting>
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<para>
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This example will produce:
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</para>
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<screen>
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<![CDATA[
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$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 /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>Convert HTML to text</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// $document should contain an HTML document.
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// This will remove HTML tags, javascript sections
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// and white space. It will also convert some
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// common HTML entities to their text equivalent.
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$search = array ("'<script[^>]*?>.*?</script>'si", // Strip out javascript
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"'<[\/\!]*?[^<>]*?>'si", // Strip out HTML tags
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"'([\r\n])[\s]+'", // Strip out white space
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"'&(quot|#34);'i", // Replace HTML entities
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"'&(amp|#38);'i",
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"'&(lt|#60);'i",
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"'&(gt|#62);'i",
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"'&(nbsp|#160);'i",
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"'&(iexcl|#161);'i",
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"'&(cent|#162);'i",
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"'&(pound|#163);'i",
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"'&(copy|#169);'i",
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"'&#(\d+);'e"); // evaluate as php
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$replace = array ("",
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"",
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"\\1",
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"\"",
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"&",
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"<",
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">",
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" ",
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chr(161),
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chr(162),
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chr(163),
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chr(169),
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"chr(\\1)");
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$text = preg_replace($search, $replace, $document);
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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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<note>
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<para>
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Parameter <parameter>limit</parameter> was added after PHP 4.0.1pl2.
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</para>
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</note>
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<para>
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See also <function>preg_match</function>,
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<function>preg_match_all</function>, and
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<function>preg_split</function>.
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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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