通过引用php更改数组的键

I believe we could change the values of an array by reference in a foreach loop like this foreach ($arr as $key => &$value)

I want to modify the keys in my case

$input = array(32 => 2, 99 => 4, 100 => 4);

foreach ($input as &$key => $value)
{
    $key = chr($key);  // I want to change the ascii character to a letter
}

I got an error saying, we cannot pass keys by reference. Any suggestions?

Try this if this works:

 foreach($input as $key => $val)
 {
   $key[] = [(string)$key => $val];
 }
 print_r($key);