PHP Manual: Prevents priority inversion

public void EventConfig::setMaxDispatchInterval ( int $max_interval , int $max_callbacks , int $min_priority )

Prevents priority inversion by limiting how many low-priority event callbacks can be invoked before checking for more high-priority events.

Note:
Available since libevent 2.1.0-alpha .

max_interval: An interval after which Libevent should stop running callbacks and check for more events, or 0 , if there should be no such interval.
max_callbacks: A number of callbacks after which Libevent should stop running callbacks and check for more events, or -1 , if there should be no such limit.
min_priority: A priority below which max_interval and max_callbacks should not be enforced. If this is set to 0 , they are enforced for events of every priority; if it's set to 1 , they're enforced for events of priority 1 and above, and so on.

Returns TRUE on success, otherwise FALSE.