Essential Books

Regular Expressions regexpPCRE

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Syntax

Parameters

Parameter | Details | —— | —— |$pattern | a string with a regular expression (PCRE pattern)|

Remarks

PHP regular expressions follow PCRE pattern standards, which are derived from Perl regular expressions.

All PCRE strings in PHP must be enclosed with delimiters. A delimiter can be any non-alphanumeric, non-backslash, non-whitespace character. Popular delimiters are ~, /, % for instance.

PCRE patterns can contain groups, character classes, character groups, look-ahead/look-behind assertions and escaped characters.

It is possible to use PCRE modifiers in the $pattern string. Some common ones are i (case insensitive), m (multiline) and s (the dot metacharacter includes newlines). The g (global) modifier is not allowed, you will use the preg_match_all function instead.

Matches to PCRE strings are done with $ prefixed numbered strings: 

<?php

$replaced = preg_replace('%hello ([a-z]+) world%', 'goodbye $1 world', 'hello awesome world');

echo $replaced; // 'goodbye awesome world'
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Regular expressions:
* Regular Expressions regexpPCRE
* Global RegExp match
* String matching with regular expressions
* Split string into array by a regular expression
* String replacing with regular expression
* String replace with callback
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