How to create a singleton background process in PHP

This article mainly introduces the method of creating a single background process in PHP, involving PHP's related operating techniques for starting, creating, judging, stopping and other processes. Friends in need can refer to it

The details are as follows:

You can start a PHP background process through the following statement:

$command = " php script.php ";
$pid = exec("nohup $command > /dev/null 2>&1 & echo $!");

nohup means that this process is independent of the created user and can run in daemon mode .

If you need this background process to run as a singleton, you can use the following method to record/judge whether the process is running

//query the database for process id
$query = "SELECT pid FROM `daemons` WHERE `pid` = '2013' LIMIT 1";
$result = mysql_query($query);
$pid = mysql_result($result, 0, 'pid');
//check if the process is running
exec("ps $pid", $pState);
if((count($pState) >= 2) && !empty($pid))
{
echo "RUNNING";
}
else
{
echo "INACTIVE";
}

You can also write the pid to a file, but if you are in a distributed task environment, it is better to put it in the database

Stop a background process:

//check if the process from the database is running
exec("ps $pid", $pState);
if((count($pState) >= 2))
{
//if the process is running, kill it
exec("kill $pid");
//update database row with an empty process id
}

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