Is is_null still slow?

bench.php

<?php
$null = null;
$notNull = 123;

$is_null = function($value) {
    for($i = 0; $i < 1000000; $i++) {
        $result = is_null($value);
    }   
    return "is_null";
};

$equal_null = function($value) {
    for($i = 0; $i < 1000000; $i++) {
        $result = ($value === null);
    }   
    return "===";
};

function bench($value, $callback) {
    $start = microtime(true);
    $name = $callback($value);
    $end = microtime(true);
    $duration = ($end - $start) * 1000;

    echo var_export($value, true) . " testing for $name, took $duration ms\n";
}

bench($null, $is_null);
bench($null, $equal_null);
bench($notNull, $is_null);
bench($notNull, $equal_null);

-> php bench.php 
NULL testing for is_null, took 5324.5060443878 ms
NULL testing for ===, took 180.72295188904 ms
123 testing for is_null, took 5317.1510696411 ms
123 testing for ===, took 178.15494537354 ms

Yes it's still slow.

1k calls to is_null is 5ms slower than using strict equality checks.