PHP script scheduler Jerrata Backbone adds a web-based user interface
to complement its existing featureset, including the ability to queue
PHP scripts to run per-webpage and per-directory. Backbone also
supports tiered scheduling, in which scripts tied to a parent directory
run before scripts tied to a child directory.

Use Backbone as a hands-on CMS, a PHP Crontab, or a tool for rapid Web
development.

See http://backbone.jerrata.com/ for more information and a 10-day
Evaluation Version download of the system attracting such testimonials
as 'A Great Tool' and 'a viable option to Cron.'