Even the most experienced developer needs to test if his regular expressions work as expected. That’s a little pain in the neck, but there is an interesting website developed by gskinner that can help us in that task:
Another cool website to learn regular expressions: www.regular-expressions.info
Useful Regular Expressions
Regular expression for Validating Emails:
preg_match('/\b[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}\b/',$mail);