(PECL libevent >= 0.0.2)
event_base_priority_init — Set the number of event priority levels
$event_base
   , int $npriorities
   )Sets the number of different event priority levels.
   By default all events are scheduled with the same priority
   (npriorities/2). 
   Using event_base_priority_init() you can change the number 
   of event priority levels and then set a desired priority for each event.
  
event_baseValid event base resource.
nprioritiesThe number of event priority levels.
   event_base_priority_init() returns TRUE on success or FALSE on error.