kritya

This is a simple code but idk y it is not working i want to return a error if user has left any field empty. and a code to execute if everything is.
If any one can give me ajax form validation script it would be better.

<?phpinclude("global.php");$username = $_POST["username"];$dsiplayName = $_POST["displayName"];$pass = $_POST["password"];$pass2 = $_POST["password2"];$age = $_POST["age"];if($username==NULL || $diplayName==NULL || $pass==NULL || $pass2==NULL || $age==NULL){ echo "Fine";}else{ echo "Username not entered";}?>

the function is post only i checked that i know that things isset function.
But the isset again only worked with direct post variable only what the problem is there idk with variable declarations but it looks fine i still want some ajax script for form validation but could not find a good one for checking email is of correct format and it does not post's the data untill everything is fine and i dont want any pop box. with yes or no things

If any one could find that for me or write that for one that would be great that is the only problem in my site.