What is happening is that linux doesn't know how to run a .php file natively.
You need to install the php command line interpreter (CLI) and EITHER
rewrite your cron job as follows:
30 11 * * * php /home/pipsquea/www/thanx.php
OR keep the cron job the same and insert the following at the very top of your .php file:
There's a tutorial here:
Don't Stand on your head - you'll get footprints in your hair