$queue = new FastPriorityQueue();
$queue->insert('a', 0);
$queue->insert('b', 1);
foreach ($queue as $value) {echo $value;} // here we fall into an infinite loop

$queue = new FastPriorityQueue();
$queue->insert('a1', 1);
$queue->insert('a2', 1);
$queue->insert('b2', 2);
$queue->remove('a1');
echo $queue->extract(); // it prints 'a2' but should 'b2'

$queue = new FastPriorityQueue();
$queue->insert('a1', 1);
$queue->insert('a2', 1);
$queue->insert('a3', 1);
$queue->remove('a2');
echo $queue->extract(); // it prints 'a3' but should 'a1', 'a1' is lost

$queue = new FastPriorityQueue();
$queue->insert('a', 1);
$queue->insert('b', 2);
$queue->remove('b');
echo $queue->extract(); // it prints an empty string but should 'a'
echo $queue->count();   // it prints 0, but there is still one element in the queue
echo $queue->extract(); // it prints 'a' which should happen when the `extract()` method was called the first time