Benchmark of call_user_func_array vs switch optimization vs argument unpacking syntax

bench.php

<?php error_reporting(E_ALL);

function test() {}

$nIter = 1000000;
$argNums = [0, 1, 2, 3, 4, 5, 100];

$func = 'test';

foreach ($argNums as $argNum) {
    $args = $argNum == 0 ? [] : array_fill(0, $argNum, null);

    $startTime = microtime(true);
    for ($i = 0; $i < $nIter; ++$i) {
        call_user_func_array($func, $args);
    }
    $endTime = microtime(true);
    echo "cufa   with $argNum args took ", $endTime - $startTime, "\n";

    $startTime = microtime(true);
    for ($i = 0; $i < $nIter; ++$i) {
        switch (count($args)) {
            case 0: $func(); break;
            case 1: $func($args[0]); break;
            case 2: $func($args[0], $args[1]); break;
            case 3: $func($args[0], $args[1], $args[2]); break;
            case 4: $func($args[0], $args[1], $args[2], $args[3]); break;
            case 5: $func($args[0], $args[1], $args[2], $args[3], $args[4]); break;
            default: call_user_func_array($func, $args); break;
        }
    }
    $endTime = microtime(true);
    echo "switch with $argNum args took ", $endTime - $startTime, "\n";

    $startTime = microtime(true);
    for ($i = 0; $i < $nIter; ++$i) {
        if (PHP_VERSION_ID >= 50600) {
            $func(...$args);
        }
    }
    $endTime = microtime(true);
    echo "unpack with $argNum args took ", $endTime - $startTime, "\n";
}

results

// RUN 1:
cufa   with 0 args took 0.51093697547913
switch with 0 args took 0.25961208343506
unpack with 0 args took 0.16498208045959
cufa   with 1 args took 0.58492302894592
switch with 1 args took 0.32328605651855
unpack with 1 args took 0.17757987976074
cufa   with 2 args took 0.62471890449524
switch with 2 args took 0.38140821456909
unpack with 2 args took 0.18650889396667
cufa   with 3 args took 0.67326211929321
switch with 3 args took 0.42645883560181
unpack with 3 args took 0.19748115539551
cufa   with 4 args took 0.71092510223389
switch with 4 args took 0.46344208717346
unpack with 4 args took 0.20987296104431
cufa   with 5 args took 0.75272703170776
switch with 5 args took 0.50403499603271
unpack with 5 args took 0.21983790397644
cufa   with 100 args took 4.6691329479218
switch with 100 args took 5.0100290775299
unpack with 100 args took 1.3475320339203

// RUN 2:
cufa   with 0 args took 0.51002717018127
switch with 0 args took 0.25696516036987
unpack with 0 args took 0.16168093681335
cufa   with 1 args took 0.58382201194763
switch with 1 args took 0.32041001319885
unpack with 1 args took 0.17517805099487
cufa   with 2 args took 0.62337493896484
switch with 2 args took 0.38088703155518
unpack with 2 args took 0.18605399131775
cufa   with 3 args took 0.67131018638611
switch with 3 args took 0.42596197128296
unpack with 3 args took 0.19695591926575
cufa   with 4 args took 0.71094298362732
switch with 4 args took 0.46291899681091
unpack with 4 args took 0.20937609672546
cufa   with 5 args took 0.75075888633728
switch with 5 args took 0.50380516052246
unpack with 5 args took 0.2197151184082
cufa   with 100 args took 4.6559550762177
switch with 100 args took 5.0126330852509
unpack with 100 args took 1.3509678840637

// RUN 3:
cufa   with 0 args took 0.5332179069519
switch with 0 args took 0.28537201881409
unpack with 0 args took 0.18562912940979
cufa   with 1 args took 0.60794401168823
switch with 1 args took 0.34805607795715
unpack with 1 args took 0.19937896728516
cufa   with 2 args took 0.6473650932312
switch with 2 args took 0.40976810455322
unpack with 2 args took 0.21083498001099
cufa   with 3 args took 0.6942150592804
switch with 3 args took 0.45553708076477
unpack with 3 args took 0.22113919258118
cufa   with 4 args took 0.73241019248962
switch with 4 args took 0.49041199684143
unpack with 4 args took 0.23208904266357
cufa   with 5 args took 0.7748589515686
switch with 5 args took 0.53174185752869
unpack with 5 args took 0.24371910095215
cufa   with 100 args took 4.7278261184692
switch with 100 args took 5.0705368518829
unpack with 100 args took 1.3685908317566