Improve performance of multi-array array_map()

[ndossche]

For this benchmark script:

<?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]);
}

On an i7-4790:

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

On an i7-1185G7:

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