PHP native with algoritms vs C++ on PHP

for.php

<?php declare(strict_types=1);

var_dump('for, 1000000 iteration');



$start=microtime(true);
for ($j = 0; $j < 1000000; $j++) {

    $str8Byte = 'Str8byte';

    $str1KB = $str8Byte;
    # 8B = 2^3, 1KB = 2^10
    for ($i = 3; $i < 10; $i++) {
        $str1KB = $str1KB.$str1KB;
    }

    $tenKBData = str_repeat($str1KB, 10);

}
$end = microtime(true);
var_dump($end - $start);

func.php

<?php declare(strict_types=1);

var_dump('func, 1000000 iteration');



$start=microtime(true);
for ($j = 0; $j < 1000000; $j++) {
    $start=microtime(true);
    $str8Byte = 'Str8byte';

    $tenKBData = str_repeat($str8Byte, 1280);

}
$end = microtime(true);
var_dump($end - $start);

run.txt

string(22) "for, 1000000 iteration"
float(0.61288499832153)

string(23) "func, 1000000 iteration"
float(3.814697265625E-6)

string(22) "for, 1000000 iteration"
float(0.6605429649353)

string(23) "func, 1000000 iteration"
float(4.0531158447266E-6)

string(22) "for, 1000000 iteration"
float(0.70987796783447)

string(23) "func, 1000000 iteration"
float(5.0067901611328E-6)

string(22) "for, 1000000 iteration"
float(0.62938618659973)

string(23) "func, 1000000 iteration"
float(5.0067901611328E-6)