View file new_fo/new_fo/test.php

<?php
$m = 'jkfd.gj.85489.3gp.sdiud9009dg.jpf'; 
$ex_m = explode('.',$m); 
$c_m = count($ex_m); 
$lost_m = $c_m - 1; 
$ex_m[$lost_m]
?>