Have the file being run by the cronjob affect a file and then look at the last time the file was touched. You could do this by rediecting the output of the file, this would have the added benifit of keeping a log of the files activities (assuming you're echoing debug information)
/usr/bin/php -q ./thefile.php &> thefile.log
The &> re-directs both stdout and stderr to the same file, in this case thefile.log. If you don't want to record stderr you could just use >
HTH
Bubble
PS. In future could you NOT use a DSL!!