Fuck it, I'm PHP!

a.php

$a = ['item0', 'item1', 'item2', 'item3', 'item4', 'item5'];
$b = [2, 3];

print_r($a);

$t = array_flip($b);
$r = array_filter($a, function($i) use ($t) {
  return !isset($t[$i]);
}, ARRAY_FILTER_USE_KEY);

$s = [];
for ($i = 0, $l = count($a); $i < $l; $i++) {
  if (!isset($t[$i])) $s[] = $a[$i];
}

print_r($s);
var_dump($s[2]);

print_r($r);
var_dump($r[2]);



print_r(array_values($r));

b..php

<?php

$a = ['a', 'b', 'c', 'd'];
$b = [1, 2];
$r = [];
$j = 0;

for ($i = 0, $j = 0, $al = count($a), $bl = count($b); $i < $al; $i++) {
  if ($j < $bl && $i == $b[$j]) {
    $j++;
  } else {
    $r[] = $a[$i];
  }
}

print_r($r);

output

Array
(
    [0] => item0
    [1] => item1
    [2] => item2
    [3] => item3
    [4] => item4
    [5] => item5
)
Array
(
    [0] => item0
    [1] => item1
    [2] => item4
    [3] => item5
)
string(5) "item4"
Array
(
    [0] => item0
    [1] => item1
    [4] => item4
    [5] => item5
)
<br />
<b>Notice</b>:  Undefined offset: 2 in <b>[...][...]</b> on line <b>20</b><br />
NULL
Array
(
    [0] => item0
    [1] => item1
    [2] => item4
    [3] => item5
)