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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@318659 c90b9560-bf6c-de11-be94-00142212c4b1
114 lines
3.5 KiB
XML
114 lines
3.5 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<article xml:id="reference.pcre.pattern.posix" xmlns="http://docbook.org/ns/docbook">
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<title>Differences from POSIX regex</title>
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<para>
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As of PHP 5.3.0, the <link linkend="book.regex">POSIX Regex</link> extension
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is deprecated. There are a number of differences between POSIX regex and
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PCRE regex. This page lists the most notable ones that are necessary to
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know when converting to PCRE.
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</para>
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<para>
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<orderedlist>
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<listitem>
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<simpara>
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The PCRE functions require that the pattern is enclosed by <link
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linkend="regexp.reference.delimiters">delimiters</link>.
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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Unlike POSIX, the PCRE extension does not have dedicated functions for
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case-insensitive matching. Instead, this is supported using the
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<emphasis>i</emphasis> (<literal>PCRE_CASELESS</literal>) <link
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linkend="reference.pcre.pattern.modifiers">pattern modifier</link>. Other
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pattern modifiers are also available for changing the matching strategy.
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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The POSIX functions find the longest of the leftmost match, but PCRE
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stops on the first valid match. If the string doesn't match at all it
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makes no difference, but if it matches it may have dramatic effects on
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both the resulting match and the matching speed.
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</simpara>
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<simpara>
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To illustrate this difference, consider the following example from
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"Mastering Regular Expressions" by Jeffrey Friedl. Using the pattern
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<literal>one(self)?(selfsufficient)?</literal> on the string
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<literal>oneselfsufficient</literal> with PCRE will result in matching
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<literal>oneself</literal>, but using POSIX the result will be the full
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string <literal>oneselfsufficient</literal>. Both (sub)strings match the
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original string, but POSIX requires that the longest be the result.
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</simpara>
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</listitem>
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</orderedlist>
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</para>
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<para>
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<table>
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<title>Function replacements</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>POSIX</entry>
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<entry>PCRE</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><function>ereg_replace</function></entry>
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<entry><function>preg_replace</function></entry>
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</row>
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<row>
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<entry><function>ereg</function></entry>
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<entry><function>preg_match</function></entry>
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</row>
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<row>
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<entry><function>eregi_replace</function></entry>
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<entry><function>preg_replace</function></entry>
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</row>
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<row>
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<entry><function>eregi</function></entry>
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<entry><function>preg_match</function></entry>
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</row>
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<row>
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<entry><function>split</function></entry>
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<entry><function>preg_split</function></entry>
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</row>
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<row>
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<entry><function>spliti</function></entry>
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<entry><function>preg_split</function></entry>
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</row>
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<row>
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<entry><function>sql_regcase</function></entry>
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<entry><emphasis>No equivalent</emphasis></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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</article>
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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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