In a cron job, when you want to execute a PHP script, you would often use the php command. On the cloud however, we provide three versions of PHP (5.2, 5.3 and 5.4), meaning you need to specify which version you want to execute your cron job with. If you just use php your code will be executed by PHP 5.2.
The version binaries are:
PHP 5.2: /usr/bin/php
PHP 5.3: /usr/bin/php-5.3
PHP 5.4: /usr/bin/php-5.4