E-mail validering

function IsValidEmailAddress($email){
    return preg_match("/^[a-z0-9]+[a-z0-9_-]+@[a-z0-9]+[a-z0-9.-]+[a-z0-9]+.[a-z]{2,4}$/i", $email);
}

if (!preg_match("/^[a-z0-9_]+@[a-z0-9\-]+\.[a-z0-9\-\.]+$/i", $email)) {

<?php
function IsValidEmailAddress($email){
    return preg_match("/^[a-z0-9]+[a-z0-9_-]+@[a-z0-9]+[a-z0-9.-]+[a-z0-9]+.[a-z]{2,4}$/i", $email);
}

$str1 = "olebole@dengodecode.museum";
$str2 = "ronols@olsensweb.dk";
$fejl = "fejl@@gir.ingen.mening.dk";

echo IsValidEmailAddress($str1);
echo "<br />";
echo IsValidEmailAddress($str2);
echo "<br />";
echo IsValidEmailAddress($fejl);
?>

<?php
function IsValidEmailAddress($email){
    return preg_match("/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}$/i", $email);
}
// lovlige
$str1 = "olebole@den.gode.code.museum";
$str2 = "ron.ols@olsensweb.dk";
$str3 = "ronols@test.olsensweb.dk";
// ulovlig
$fejl = "fejl@@gir.ingen.mening.dk"; // dobbelt @
$fejl1 = "fejl@gir.ingen.mening.d"; // ulovlig tld, 
echo IsValidEmailAddress($str1); echo "<br />";
echo IsValidEmailAddress($str2); echo "<br />";
echo IsValidEmailAddress($str3); echo "<br />";
echo IsValidEmailAddress($fejl); echo "<br />";
echo IsValidEmailAddress($fejl1);
?>