I have a image button that I would like to use, but when I changed my form button type to image, my PHP form will not process:

PHP Code:
<?php if (array_key_exists('gotoreview'$_POST)) {
    echo 
'you click the gotoreview button';
}
?>
HTML Code:
<form id="form1" name="form1" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<p style="font-weight: normal"><input type="image" name="gotoreview" id="gotoreview" alt="" style="float: right; margin-right: 3px" src="http://www.sitepoint.com/forums/images/review-and-complete.png" height="33" width="135" />
</form>
Thanks for the help!