how to schedule sent email in my codeigniter project

easiest way to do cron -- is if your hosting company has a tool for it.
like if you are using cpanel, the cron tool is very easy to use.

How to use in my application and how to execute cli with PHP code

A cron job is a server configuration that tells the server to run a task at certain times.

From the terminal, you access the place to create cron jobs by typing "crontab -e".

Many tutorials exist for creating cron jobs, but in general the job is scheduled by choosing a time for it to run, and providing a command to run. CodeIgniter makes running cron jobs easy, because of the CLI mentioned above.

So, you just create the functionality you want in a controller, and then point your cron job at it.

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