PHP Programming/Daemonization
A daemon is an application that runs in the background, as opposed to being directly operated by the user. Examples of daemons are Cron and MySQL.
Daemonizing a process with PHP is very easy, and requires PHP 4.1 or higher compiled with --enable-pcntl.
Building a Daemon
[edit | edit source]We'll start with set_time_limit(0) to let our script run indefinitely. Next, we fork the PHP process with pcntl_fork(). Finally, we use posix_setsid() to tell the child process to run in the background as a session leader.
<?set_time_limit(0);// Remove time limit if(pcntl_fork()){// Fork processprint"Daemon running.";}else{$sid=posix_setsid();// Make child process session leaderif($sid<0)exit;while(true){// Daemon script goes here}}?>The code inside the while statement will run in the background until exit or die is explicitly called.
Applications
[edit | edit source]While daemonizing a script can be useful, it is not appropiate for every script. If a script only needs to be executed at a certain time, it can take advantage of Cron for scheduled execution.
