php regexp vs native functions

bench.php

<?php
$calibration = benchmark(function()
{
});
$benchmark = benchmark(function()
{
    $text = "Text oppa post lost kost most dust past";
    $char = "p";
    
    if (mb_strlen($char) > 1) {
        return -1;
    }
    
    return substr_count($text, $char);
});

$benchmark2 = benchmark(function()
{
    $text = "Text oppa post lost kost most dust past";
    $char = "p";
    
    if (strlen($char) > 1) {
        return -1;
    }
    $re = "/($char)/";
    preg_match_all($re, $text, $matches, PREG_SET_ORDER, 0);
    
    return count($matches);
});

echo "Calibration run: " . number_format($calibration) . "/sec\n";
echo "Benchmark substr_count run: " . number_format($benchmark) . "/sec\n";
echo "Benchmark regexp run: " . number_format($benchmark2) . "/sec\n";
echo 'Approximate code substr_count execution time (seconds): ' . number_format((1 / $benchmark) - (1 / $calibration), 10) . PHP_EOL;
echo 'Approximate code regexp execution time (seconds): ' . number_format((1 / $benchmark2) - (1 / $calibration), 10) . PHP_EOL;

function benchmark($x)
{
    $start = $t = microtime(true);
    $total = $c = $loop = 0;
    while (true) {
        $x();
        $c++;
        $now = microtime(true);
        if ($now - $t > 1) {
            $loop++;
            $total += $c;
            list($t, $c) = array(
                microtime(true),
                0
            );
        }
        if ($now - $start > 2) {
            return round($total / $loop);
        }
    }
}

results.log

Alexanders-MacBook-Pro:~ sanasol$ php bench.php 

Calibration run: 10,551,252/sec
Benchmark substr_count run: 4,608,441/sec
Benchmark regexp run: 1,472,625/sec
Approximate code substr_count execution time (seconds): 0.0000001222
Approximate code regexp execution time (seconds): 0.0000005843

Calibration run: 10,686,848/sec
Benchmark substr_count run: 4,735,970/sec
Benchmark regexp run: 1,478,864/sec
Approximate code substr_count execution time (seconds): 0.0000001176
Approximate code regexp execution time (seconds): 0.0000005826

Calibration run: 10,579,233/sec
Benchmark substr_count run: 4,732,437/sec
Benchmark regexp run: 1,446,469/sec
Approximate code substr_count execution time (seconds): 0.0000001168
Approximate code regexp execution time (seconds): 0.0000005968

Calibration run: 10,673,012/sec
Benchmark substr_count run: 4,644,348/sec
Benchmark regexp run: 1,477,172/sec
Approximate code substr_count execution time (seconds): 0.0000001216
Approximate code regexp execution time (seconds): 0.0000005833