If you have to intersect arrays of unique values then using array_intersect_key is about 20 times faster, just have to flip the key value pairs of the arrays, then flip the result again.
<?php
$one = range(1, 250000);
$two = range(50000, 150000);
$start = microtime(true);
$intersection = array_intersect($one, $two);
echo "Did it in ".( microtime(true) - $start )." seconds.\n";
$start = microtime(true);
$intersection = array_flip(array_intersect_key(array_flip($one), array_flip($two)));
echo "Did it in ".( microtime(true) - $start )." seconds.\n";
?>
Did it in 0.89163708686829 seconds.
Did it in 0.038213968276978 seconds.
