I needed to setup a persistent cron job on my QNAP TS-431 that would run a PHP script (actually the script that let’s me always know what the IP address of my home router is from anywhere in the world). However, the QNAP has the php executable buried and the directory is not in the $PATH environment variable. It’s not too hard to find though, if you need to run a PHP script just do this:

mnt/ext/opt/apache/bin/php /path/to/some-php-script.php