Benchmark SQRT vs EXP 0.5

<?php
$times = [];
for ($x = 0; $x < 10; $x++) {
    $start = microtime(true);
    for ($i = 0; $i < 1e7; $i++) {
        $a = sqrt($i);
    }
    $times[$x] = microtime(true) - $start;
    echo 'sqrt: ', $times[$x], PHP_EOL;
}
$avg1 = array_sum($times);
echo 'average: ', $avg1 / 10, PHP_EOL;

echo str_repeat('=', 70), PHP_EOL;

$times = [];
for ($x = 0; $x < 10; $x++) {
    $start = microtime(true);
    for ($i = 0; $i < 1e7; $i++) {
        $a = $i ** .5;
    }
    $times[$x] = microtime(true) - $start;
    echo 'exp: ', $times[$x], PHP_EOL;
}
$avg2 = array_sum($times);
echo 'average: ', $avg2 / 10, PHP_EOL;

echo 'ratio: ', max($avg1, $avg2) / min($avg1, $avg2), PHP_EOL;

/**
sqrt: 1.6493890285492
sqrt: 1.6189279556274
sqrt: 1.6098041534424
sqrt: 1.6156868934631
sqrt: 1.6098020076752
sqrt: 1.5989210605621
sqrt: 1.6093671321869
sqrt: 1.604642868042
sqrt: 1.6029407978058
sqrt: 1.6166899204254
average: 1.613617181778
======================================================================
exp: 0.55803894996643
exp: 0.55601787567139
exp: 0.55864214897156
exp: 0.56141209602356
exp: 0.55727696418762
exp: 0.55723094940186
exp: 0.55681586265564
exp: 0.55726480484009
exp: 0.56148099899292
exp: 0.5568699836731
average: 0.55810506343842
ratio: 2.8912426843732
*/