I am not sure what you are trying to do, but by default there should be a php CLI binary at /usr/local/bin/php.
So if you wanted to execute a PHP Script with Cron, do this:
00 00 * /usr/local/bin/php /path/to/script.php 1> /dev/null 2> /dev/null
That will run every night at midnight. But you should start by making sure the binary exists.