Sets the mode of extraction
$flags
flags
Defines what is extracted by SplPriorityQueue::current, SplPriorityQueue::top and SplPriorityQueue::extract.
SplPriorityQueue::EXTR_DATA
SplPriorityQueue::EXTR_PRIORITY
SplPriorityQueue::EXTR_BOTH
The default mode is SplPriorityQueue::EXTR_DATA.
Returns the flags of extraction.