Remix the string based on array - php

Question

I have a simple whiteboard question:
Create a function that takes both a string and an array of numbers as arguments. Rearrange the letters in the string to be in the order
specified by the index numbers. Return the "remixed" string. Examples
remix("abcd", [0, 3, 1, 2]) ➞ "adbc"
I submitted my code but it's not being accepted and I am unable to see why. I wrote:
function remix($str, $arr) {
$strArr = str_split($str);
for($i = 0; $i < count($strArr); $i++) {
$arr[$i] = $strArr[$arr[$i]];
}
return implode("", $arr);
}
remix("computer", [0, 2, 1, 5, 3, 6, 7, 4]); // ➞ "cmourpte"
Can anyone see something wrong with it? It's always regular characters, no special cases FYI. Very confused.

Answer 1

It looks like the assignment part is putting the value the wrong way round (i.e. it should be assigning the char at position $i to $arr[$i])...
function remix($str, $arr) {
$strArr = str_split($str);
for($i = 0; $i < count($strArr); $i++) {
$strArr[$arr[$i]] = $str[$i];
}
return implode("", $strArr);
}
which for
echo remix("PlOt", [1, 3, 0, 2]).PHP_EOL;
echo remix("computer", [0, 2, 1, 5, 3, 6, 7, 4]);
gives
OPtl
cmourpte
Just to check, this passes the test.

Answer 2

Well it would seem you missed that the remix was giving an incorrect result.
But I would have done it this way as by default a PHP String is in fact an array already.
function remix($str, $arr) {
$mixed = '';
foreach ($arr as $i) {
$mixed .= $str[$i];
}
return $mixed;
}
echo remix("computer", [0, 2, 1, 5, 3, 6, 7, 4]);
RESULT
cmotperu
In fact if this is the question, the stated answers are wrong in ALL cases.
Create a function that takes both a string and an array of numbers as arguments.
Rearrange the letters in the string to be in the order specified by the index numbers.
Return the "remixed" string.
Examples
remix("abcd", [0, 3, 1, 2]) ➞ "acdb"
The string you'll be returning will have: "a" at index 0, "b" at index 3, "c" at index 1, "d" at index 2, because the order of those characters maps to their corresponding numbers in the index array.
remix("PlOt", [1, 3, 0, 2]) ➞ "OPtl"
remix("computer", [0, 2, 1, 5, 3, 6, 7, 4]) ➞ "cmourpte"