enum Pcntl\QosClass
{
case Background
; //
Runs the process after all high-priority ones had ran their courses.
case Default
; //
Runs the process after all high-priority processes but before the low-priority ones.
case UserInteractive
; //
Runs the process as the highest priority level.
case UserInitiated
; //
Runs the process at high priority level but below UserInteractive ones.
}