php array_intersect() efficiency

Question

consider the below script. two arrays with only three values.when i compare these two arrays using array_intersect(). the result is fast.

Answer 1

The fastest solution I found:

function arrayIntersect($arrayOne, $arrayTwo) {
        $index = array_flip($arrayOne);
        $second = array_flip($arrayTwo);

        $x = array_intersect_key($index, $second);

        return array_flip($x);
}

Tests I have made looks like below:

function intersect($arrayOne, $arrayTwo)
{
    $index = array_flip($arrayOne);
    foreach ($arrayTwo as $value) {
        if (isset($index[$value])) unset($index[$value]);
    }
    foreach ($index as $value => $key) {
        unset($arrayOne[$key]);
    }

    return $arrayOne;
}

function intersect2($arrayOne, $arrayTwo)
{
    $index = array_flip($arrayOne);
    $second = array_flip($arrayTwo);

    $x = array_intersect_key($index, $second);

    return array_flip($x);

}

for($i =0; $i < 1000000; $i++) {
    $one[] = rand(0,1000000);
    $two[] = rand(0,100000);
    $two[] = rand(0,10000);
}

$one = array_unique($one);
$two = array_unique($two);

$time_start = microtime(true);
$res = intersect($one, $two);
$time = microtime(true) - $time_start;

echo "Sort time $time seconds 'intersect' \n";


$time_start = microtime(true);
$res2 = array_intersect($one, $two);
$time = microtime(true) - $time_start;

echo "Sort time $time seconds 'array_intersect' \n";


$time_start = microtime(true);
$res3 = intersect2($one, $two);
$time = microtime(true) - $time_start;

echo "Sort time $time seconds 'intersect2' \n";

Results from php 5.6 :

Sort time 0.77021193504333 seconds 'intersect' 
Sort time 6.9765028953552 seconds 'array_intersect' 
Sort time 0.4631941318512 seconds 'intersect2'