Replacing every number in a string with a random char

Question

I want to replace every number in a string like ABC123EFG with another random char.
My idea was to generate a random string with the number of all numbers in $str and replace every digit by $array[count_of_the_digit], is there any way to do this without a for-loop, for example with regex?

$count = preg_match_all('/[0-9]/', $str);
$randString = substr(str_shuffle(str_repeat("abcdefghijklmnopqrstuvwxyz", $count)), 0, $count);
$randString = str_split($randString);
$str = preg_replace('/[0-9]+/', $randString[${n}], $str); // Kinda like this (obviously doesnt work)

Answer 1

You could use preg_replace_callback()

$str = 'ABC123EFG';

echo preg_replace_callback('/\d/', function(){
  return chr(mt_rand(97, 122));
}, $str);

It would output something like:

ABCcbrEFG

If you want upper case values, you can change 97 and 122 to their ASCII equivalent of 64 to 90.