Change the priority of any process

pcntl_setpriority(int $priority, ?int $process_id = null, int $mode = PRIO_PROCESS): bool

pcntl_setpriority() sets the priority of process_id.

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.
process_id: If null, the process id of the current process is used.
mode: One of PRIO_PGRP, PRIO_USER, PRIO_PROCESS, PRIO_DARWIN_BG or PRIO_DARWIN_THREAD.

Returns true on success or false on failure.

Version	Description
8.0.0	`process_id` is nullable now.

pcntl_setpriority