Measure array unpack vs. array_merge

0_output.log

Array Unpack
user:	  4.355 ms
system:	      0 ms
wait:	     25 ms
total:	  4.381 ms

Array Merge
user:	  6.798 ms
system:	      0 ms
wait:	      7 ms
total:	  6.805 ms

1_measure.php

<?php

$measure = static function (callable $lambda) {
    $startHrTime = hrtime(true);
    $rUsage = getrusage();
    $startUTime = $rUsage['ru_utime.tv_usec'] + $rUsage['ru_utime.tv_sec'] * 1000000;
    $startSTime = $rUsage['ru_stime.tv_usec'] + $rUsage['ru_stime.tv_sec'] * 1000000;

    $lambda();

    $rUsage = getrusage();
    $user   = ($rUsage['ru_utime.tv_usec'] + $rUsage['ru_utime.tv_sec'] * 1000000 - $startUTime) / 1000;
    $system = ($rUsage['ru_stime.tv_usec'] + $rUsage['ru_stime.tv_sec'] * 1000000 - $startSTime) / 1000;
    $total  = (hrtime(true) - $startHrTime) / 1000000;
    $wait   = $total - ($user + $system);

    $measurements = [
        'user'   => $user,
        'system' => $system,
        'wait'   => $wait,
        'total'  => $total,
    ];
    $format = static function (float $timeInMs) {
        return str_pad(number_format($timeInMs, 0, ',', '.') . ' ms', 10, ' ', STR_PAD_LEFT);
    };

    foreach ($measurements as $header => $value) {
        echo "${header}:\t" . $format($value) . PHP_EOL;
    }
    echo PHP_EOL;
};

const REPEAT = 100000000;
echo "Array Unpack\n";
$measure(static function () {
    $item = 'foo';
    $items = ['bar', 'baz'];
    for ($x = 0; $x < REPEAT; ++$x) {
        $foo = [$item, ...$items];
    }
});

echo "Array Merge\n";
$measure(static function () {
    $item = 'foo';
    $items = ['bar', 'baz'];
    for ($x = 0; $x < REPEAT; ++$x) {
        $foo = array_merge([$item], $items);
    }
});