AgedFirsthandKeyboard created by joshghent - https://repl.it/@joshghent/AgedFirsthandKeyboard

main.php

$string = "floccinaucinihilipilification";
$characters = array_unique(str_split($string));

$count = [];

foreach($characters as $char) {
  $count[$char] = substr_count($string, $char);
}

// Order the array
arsort($count);

echo json_encode($count);