Job Alert System

Thank you visualsol for the idea on frontend implementation. But what I need is how to set up the cronjob, not really how to save the searched terms to the user's profile. Once the searched terms are stored, the code to implement the cronjob is what I have no idea how? Any help is appreciated.

You can write a Controller, which is doing that search task.
Make sure, that the php script is running on the cli. (https://www.codeigniter.com/userguide2/general/cli.html)
(so you prevent calls from the browser/other people)
Than you can run the php script on the cli on your server.
When you have a linux server, you could write a sh-script which is running the php-script.
This sh-script can you add to your Crontab.  (http://www.makeuseof.com/tag/linux-task-...explained/)