PHP: mysql_connect() won't work via command line

I have a script which calls mysql_connect() to connect to a MySQL DB. When I run the script in a browser, it works. However, when I run it from a command line I receive the following error:

Call to undefined function mysql_connect()

This seems completely paradoxical. Anyone have any ideas as how I can run it from the command line. Btw, I run it from a bash shell like so:

php /path/to/script.php