You can't just run php script in cron as linux doesn't know how to execute that file. Change permissions of that script to make it executable, and at the beginning of script add this:
Code:
#!/usr/local/bin/php -q
Another method is to call php instead of script: /usr/local/bin/php /home/whatever/public_html/blah/cronscript.php
and make sure you put full path to your php script