Validate Email address (old blog post)

valid-email.php

<?php
function validEmail($email_address){
	// First, we check that there's one @ symbol, and that the lengths are right
	if (!ereg("^[^@]{1,64}@[^@]{1,255}$", $email_address)) {
		// Email invalid because wrong number of characters in one section, or wrong number of @ symbols.
		return false;
	}
	// Split it into sections to make life easier
	$email_array = explode("@", $email_address);
	$local_array = explode(".", $email_array[0]);
	for ($i = 0; $i < sizeof($local_array); $i++) {
		if (!ereg("^(([A-Za-z0-9!#$%&'*+/=?^_`{|}~-][A-Za-z0-9!#$%&'*+/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$", $local_array[$i])) {
			return false;
		}
	}
	if (!ereg("^\[?[0-9\.]+\]?$", $email_array[1])) { // Check if domain is IP. If not, it should be valid domain name
		$domain_array = explode(".", $email_array[1]);
		if (sizeof($domain_array) < 2) {
			return false; // Not enough parts to domain
		}
		for ($i = 0; $i < sizeof($domain_array); $i++) {
			if (!ereg("^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]+))$", $domain_array[$i])) {
				return false;
			}
		}
	}
	return true;
}