Check associative string array values

Question

I have the following string array

$array = array(
    "key" => "zhcdde,hzccd,eezhg"
);

I want to get the values, split them with ',' and count the equal letters. For example only "z" and "h" are equal, since these are the only characters that occur in every string composition. I tried a few things like this

$equalLetters = 0;
foreach ($array as $key => $splitWords) {
    $words = explode(",", $splitWords);
    for ($letter = 0; $letter < strlen($words[0]); $letter++) {
        if ($words[0][$letter] == $words[1][$letter] || $words[0][$letter] == $words[2][$letter] || $words[1][$letter] == $words[2][$letter]) {
            $equalLetters++;
        }
    }
}
echo $equalLetters;

Without success. Can you guys help me ?

Answer 1

Unclear for me how the associative array factors into it, but here's how you can get the common letters in your strings:

<?php
    $string = 'zhcdde,hzccd,eezhg';
    $words = explode(',', $string);
    $letters = array_map('str_split', $words);
    $common = call_user_func_array('array_intersect', $letters);

    var_dump($common);
?>

Which outputs:

array(2) {
  [0]=>
  string(1) "z"
  [1]=>
  string(1) "h"
}