RegEx Email Address Verification

Very simple regular expression email address verification function

I built this to deal with the structure of an email address, not whether or not it had a valid TLD on the end of it or whatever. This simply checks to make sure that the address has valid email address characters to the left of an @ symbol and a valid domain name to the right.

PHP Source Code

<?php

// isValidEmail( [string] )
// returns 0 if email address is invalid
// returns 1 if email address is good
function isValidEmail( $e ) {
return preg_match( '/^[_a-z0-9-][^\<\>\@\,\;\:\\\"\[\] ]*\@([a-z0-9\-]+\.)+[a-z]{2,4}$/i', $e );
}

$msg = '';
if( !empty( $_POST['address'] ) ) {
if( isValidEmail( $_POST['address'] ) ) {
$msg = '<p style="color:#009900">Good email address!</p>';
} else {
$msg = '<p style="color:#990000">Bad email address.</p>';
}
}

?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" version="-//W3C//DTD XHTML 1.1//EN" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=utf-8" />
<link href="/includes/css/ozStyle.css.php" type="text/css" rel="stylesheet" />
<title>Email Validation Demo</title>
</head>

<body style="margin:10px">

<h1>Email Validation</h1>

<?= !empty( $msg ) ? $msg : '' ?>

<form method="post" style="margin: 0px; padding: 0px;">

<p>Email address:<br />
<input name="address" type="text" value="<?=$_POST['address']?>" size="60" maxlength="255"></p>

<p><input type="submit" value="submit" /></p>

</form>

</body>

</html>