Never mind. I figured it out.
$filename = "Last,First01010_02162005.doc";
$periodpos = explode(".", $filename);
$commapos = explode(",", $filename);
$dashpos = explode("_", $commapos[1]);
echo "<br>Lastname = ".$commapos[0];
echo "<br>Firstname =".substr($dashpos[0],0,-5);
echo "<br>ID1 =".substr($dashpos[0],-5,5);
echo "<br>ID2 =".substr($dashpos[1], 0, -4);
If you have better ideas, please let me know. Thanks.