(PHP 5, PHP 7)
pcntl_setpriority — Change the priority of any process
pcntl_setpriority ( int $priority [, int $pid = getmypid() [, int $process_identifier = PRIO_PROCESS ]] ) : bool
 pcntl_setpriority() sets the priority of pid. 
priority
 priority is generally a value in the range -20 to 20. The default priority is 0 while a lower numerical value causes more favorable scheduling. Because priority levels can differ between system types and kernel versions, please see your system's setpriority(2) man page for specific details. 
pid
If not specified, the pid of the current process is used.
process_identifier
 One of PRIO_PGRP, PRIO_USER or PRIO_PROCESS. 
 Returns true on success or false on failure. 
    © 1997–2020 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
    https://www.php.net/manual/en/function.pcntl-setpriority.php