<?php
function sum($a, $b) {
 return $a+$b;
}
$cb = sum(...);
for ($i = 0; $i < 1000000; $i++) {
 array_map($cb, [1,2,3], [4,5,6]);
}

Benchmark 1: ./sapi/cli/php x.php
 Time (mean ± σ): 171.9 ms ± 2.1 ms [User: 168.6 ms, System: 2.3 ms]
 Range (min ... max): 168.8 ms ... 176.1 ms 17 runs
 
Benchmark 2: ./sapi/cli/php_old x.php
 Time (mean ± σ): 206.3 ms ± 4.1 ms [User: 201.8 ms, System: 2.7 ms]
 Range (min ... max): 201.8 ms ... 217.3 ms 14 runs
 
Summary
 ./sapi/cli/php x.php ran
 1.20 ± 0.03 times faster than ./sapi/cli/php_old x.php

Benchmark 1: ./sapi/cli/php x.php
 Time (mean ± σ): 98.9 ms ± 2.0 ms [User: 97.3 ms, System: 1.4 ms]
 Range (min ... max): 96.3 ms ... 102.8 ms 30 runs
 
Benchmark 2: ./sapi/cli/php_old x.php
 Time (mean ± σ): 122.1 ms ± 1.0 ms [User: 120.0 ms, System: 1.9 ms]
 Range (min ... max): 120.8 ms ... 123.9 ms 24 runs
 
Summary
 ./sapi/cli/php x.php ran
 1.23 ± 0.03 times faster than ./sapi/cli/php_old x.php