Handy Regular Expressions
Split a string into words (PHP, unicode):
preg_match_all("/[\p{L}\p{M}]+/u", $string, $result, PREG_PATTERN_ORDER);
(used in the Rocket Reader plugin)
Validate an Email Address:
/(^[a-z0-9]([a-z0-9_\.\-]*)@([a-z0-9_\.\-]*)([.][a-z0-9]{2,3})$)|(^[a-z0-9]([a-z0-9_\.\-]*)@([a-z0-9_\.\-]*)(\.[a-z0-9]{2,3})(\.[a-z0-9]{2,3})*$)/i
Validate Letters Only: /^([a-zA-Z]+)$/
Validate a Dutch Postal code:
/^([0-9]{4})([A-Za-z]{2})$/
Validate an URL:
/(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/