validate graphical submit button

[Suba]

I made an image as submit button using input tag
but i dont no how to validate this button in php
////
<form?
<input type=img src=... name=sub>
</form>

<?php
if(isset($_POST['sub']
echo "hi";
?>

//// not working

plz do help me

[coopster]

Welcome to WebmasterWorld, Suba.

Form processing problem with input type=image! [webmasterworld.com]