input type='image' $_POST problem while image sa submit button

When i used <input type="image' name="submit"/> as submit button and <input type="image' name="reject"/> as Reject button in a form ,i  notice that $_POST have no information about which button is clicked...
SOLUTION
Use a hidden field and set its value using javascript using a function 'onclick'.

For example:
<form>
<input type="text" name="name"/>
<input type="image' name="submit"  onclick="confirm('submit')"/>
 <input type="image' name="reject" onclick="confirm('reject')"/> 
<input type="hidden" name="suborrej">
</form>
<script type="text/javascript">
function confirm(status)
{
document.getElementById('suborrej').value=status;
}
</script>
Now you can check using php
if($_POST['suborrej']=='submit')
{
}
else
{
}