Email addresses are one of trickiest input types to validate because there are multiple ways emails can be written according to the RFC2822 specification. You could have me@gmail.com, or me+spam@gmail.com, or “mark@server”@marksanborn.net, common on Linux/BSD systems.
A lot of times people will use a regular expression like:
(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6})
This regular expression would work for almost all email addresses but would fail for others. For example mark@gmail.co.uk would not match. Either would mark+spam@gmail.com. Which by the way is a very useful feature for email hosts that support it.
Fortunately using my favorite PHP Framework, Zend Framework, we don’t have to reinvent the proverbial wheel.
Validating an Email Address with Zend Framework
Although they managed to get the regex for validating emails correctly, this is not where the power of Zend lies. Zend gives you the ability to:
Check if the hostname actually accepts email
Configure which emails types you will accept
Validate Top Level Domains
Validate International Domains Names (for international characters)