I’ve nicely written PHP script that I’d like to run as a cron job. I’m using CentOS 4.5 as server with Apache web server. How do I setup a PHP script as a cron job?

You need to setup execute permission on a php script. You need to use chmod command to change file access permissions. Use chmod command as follows:

chmod +x scriptname.php

Also make sure you add following line to top of php script (first line should be #!/usr/bin/php):

#!/usr/bin/php

If you are using FreeBSD, use:

#!/usr/local/bin/php

#!/usr/bin/php is called as a shebang (pound bang). It execute php script using the interpreter /usr/bin/php.

Save and close the file.

Setup and run php script as a cron job

Now add cron job by typing following command:
$ crontab -e
Output:

# run everday at 10:45
45 10 * * *     /path/to/myphpscript.php

Save and close the file.