12.8. Regular Expressions

Regular expressions offer a powerful way to test strings for the presence of patterns. They use a language all their own to describe patterns, a language that consists mostly of symbols. PHP offers two types of functions for regular expressions: native and Perl-compatible. You may wish to turn to Chapter 22, which describes regular expressions in detail.

Andrei Zmievski added support to PHP for Perl-compatible regular expressions. Expressions are surrounded by delimiters, which are usually / or | characters, but can be any printable character other than a number, letter, or backslash. After the second delimiter, you may place one or more modifiers. These are letters that change the way the regular expression is interpreted. ...

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