Very simple function to validate email address in PHP (2 posts)

The function uses regular expressions to validate the format of an email address. If you have questions and suggestions please let me know!

function isValidEmail($email)
{
	if(preg_match("/[.+a-zA-Z0-9_-]+@[a-zA-Z0-9-]+.[a-zA-Z]+/", $email) == 0)
		return false;
	else
		return true;
}

Very basic email validation. I have a function that also uses regex, but also the getmxrr function that searches dns for MX records corresponding the hostname.

function check_email($email)
{

// Create the syntactical validation regular expression
$match = "^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-0-9-]+)*(\.[a-z]{2,4})$";

// Presume that the email is invalid
$valid = 0;

// Validate the syntax
if (eregi($match, $email))
{
list($username,$domain) = split("@",$email);

// Validate the domain
if (getmxrr($domain,$mxrecords))
$valid = 1;
}
else
{
$valid = 0;
}
return $valid;
}
?>