<?php
$filename = tempnam("/tmp/cnm_oders/", "order_");
$fd = fopen($filename, 'w');
$start = time();
....
fwrite($fd, "Before SQL query on line ### in file xyz.php " . time()-$start . " seconds has elapsed since the script started...");
db_query("INSERT INTO shipper_order_info (.....)")
fwrite($fd, "After SQL query on line ### in file xyz.php" . time()-$start . " seconds has elapsed since the script started...");
... script runs on...
fwrite($fd, "Before send_mail() on line ### in file xyz.php... " . time()-$start . " seconds has elapsed since the script started...");
send_mail($to, $from.....
fwrite($fd, "After send_mail() on line ### in file xyz.php... " . time()-$start . " seconds has elapsed since the script started...");
..... script runs on....
fwrite($fd "Script xyz.php finished, total time = " . time()-$start);
fclose($fd);
?>