A cron (an abbreviation for chronograph) defines a process used to execute a script, start a program, send a newsletter, backup a database, display a message, remove some unnecessary files at a specified date or time, or at a set interval. In general, any process that you want the computer to execute automatically is a cron. This article explains how you can run PHP scripts as crons.
PHP Crons and Linux
Linux has a good solution for managing processes that execute at specific times: the cron daemon (called crond). You define the scripts or commands that you want to run in “crontab” files. Crontabs represent a set of tasks performed chronologically; each line represents one entry. Each entry specifies information about how to perform a task, such as executing a script. These individual tasks are called “cron jobs.”