The boundaries.
WHAT THEY CAN DO
Run a PHP script Run a shell command Trigger a URL, where that is appropriate Run application command-line tools
WHAT THEY CANNOT DO
Run more frequently than once a minute Run something requiring interaction Guarantee exact timing under load Run if the account is suspended
TRIGGERING A URL VERSUS RUNNING A SCRIPT
Running the PHP script directly is generally better: faster, no web server involvement, no HTTP timeout.
Triggering a URL is sometimes required by an application.
THE HTTP TIMEOUT POINT
A job triggering a URL is subject to web server timeouts.
A long job run that way may be cut off partway.
RESOURCE LIMITS
Cron jobs consume your account's resources like anything else.
A heavy job at a busy time affects your site.
WHAT TO CHECK
Whether the application provides a command-line method.
Most do, and it is the better option.
