Regular expressions is a very powerful instrument to manipulate and extract strings. However not all PHP developers know how to use regular expressions, so this simple tutorial is intended to everyone who wants to learn them.

PHP has several built-in functions for dealing with regular expressions. We'll examine only the PCRE functions (preg_replace, preg_match_all), which use a Perl-compatible regular expression syntax, as they are often faster than POSIX alternatives (ereg, ereg_replace, etc.)..