(PHP 5)
pcntl_setpriority — Change the priority of any process
$priority
   [, int $pid = getmypid()
   [, int $process_identifier = PRIO_PROCESS
  ]] )
   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.
      
pidIf 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.