Run php script as daemon process

Question

I need to run a php script as daemon process (wait for instructions and do stuff). cron job will not do it for me because actions need to be taken as soon as instruction arr

Answer 1

There is more than one way to solve this problem.

I do not know the specifics but perhaps there is another way to trigger the PHP process. For instance if you need the code to run based on events in a SQL database you could setup a trigger to execute your script. This is really easy to do under PostgreSQL: http://www.postgresql.org/docs/current/static/external-pl.html .

Honestly I think your best bet is to create a Damon process using nohup. nohup allows the command to continue to execute even after the user has logged out:

nohup php myscript.php &

There is however a very serious problem. As you said PHP's memory manager is complete garbage, it was built with the assumption that a script is only executing for a few seconds and then exists. Your PHP script will start to use GIGABYTES of memory after only a few days. You MUST ALSO create a cron script that runs every 12 or maybe 24 hours that kills and re-spawns your php script like this:

killall -3 php
nohup php myscript.php &

But what if the script was in the middle of a job? Well kill -3 is an interrupt, its the same as doing a ctrl+c on the CLI. Your php script can catch this interrupt and exit gracefully using the PHP pcntl library: http://php.oregonstate.edu/manual/en/function.pcntl-signal.php

Here is an example:

function clean_up() {
  GLOBAL $lock;
  mysql_close();
  fclose($lock)
  exit();
}
pcntl_signal(SIGINT, 'clean_up');

The idea behind the $lock is that the PHP script can open a file with a fopen("file","w");. Only one process can have a write lock on a file, so using this you can make sure that only one copy of your PHP script is running.

Good Luck!