php - Multiple Submit buttons, how do determine which one was clicked? -

i have form multiple submit buttons.

each submit button img src trash can denotes delete icon messages in web based messaging mail inbox

what best way figure out submit button icon clicked can write php/mysql code delete message?

if(!empty($_post)){         // how figure out submit button has been clicked id of message delete? }  <form method="post"> <input src="http://www.foo.com/img.png" id="button_1"> <input src="http://www.foo.com/img.png" id="button_2"> <input src="http://www.foo.com/img.png" id="button_3"> <input src="http://www.foo.com/img.png" id="button_4"> ... <input src="http://www.foo.com/img.png" id="button_100"> </form> 

set value each submit button , check in php , find 1 clicked

<form method="post"> <img src="http://www.foo.com/img.png" id="button_1" name="submit_btn" value="1"> <img src="http://www.foo.com/img.png" id="button_2" name="submit_btn" value="2"> <img src="http://www.foo.com/img.png" id="button_3" name="submit_btn" value="3"> <img src="http://www.foo.com/img.png" id="button_4" name="submit_btn" value="4"> ... <img src="http://www.foo.com/img.png" id="button_100" name="submit_btn" value="100"> </form> 

echo $_post['submit_btn']; give value of submit button clicked