mt_rand vs chr vs string concatenation

benchmark.php

<?php
function timer(callable $block) {
    $start = microtime(true);
    for ($i = 0; $i < 100000; ++$i) {
        $block();
    }
    $end = microtime(true);
    return $end - $start;
}


$tests = [
    'mt_rand only' => timer(function() {
        for ($i = 0; $i < 32; ++$i) {
           mt_rand(0, 255);
        }
    }),
    'mt_rand and chr' => timer(function() {
        for ($i = 0; $i < 32; ++$i) {
           chr(mt_rand(0, 255));
        }
    }),
    'mt_rand and chr and string concatenation' => timer(function() {
        $buf = '';
        for ($i = 0; $i < 32; ++$i) {
           $buf .= chr(mt_rand(0, 255));
        }
    })
];

asort($tests);

var_dump($tests);

result.txt

array(3) {
  ["mt_rand only"]=>
  float(0.45156311988831)
  ["mt_rand and chr"]=>
  float(0.66792511940002)
  ["mt_rand and chr and string concatenation"]=>
  float(0.80100607872009)
}