Table of Contents
Pattern Modifiers — Describes possible modifiers in regex patterns
Pattern Syntax — Describes PCRE regex syntax
preg_grep — Return array entries that match the pattern
preg_match_all — Perform a global regular expression match
preg_match — Perform a regular expression match
preg_quote — Quote regular expression characters
preg_replace_callback — Perform a regular expression search and replace using a callback
preg_replace — Perform a regular expression search and replace
preg_split — Split string by a regular expression
для урл
preg_match("/^(http:\/\/)?([^\/]+)/i",$host,$matches);
echo $matches[2];
и тп.
вобщем - в пхп реализоны и посикс и пцре выражения.