387. First Unique Character in a String

class Solution {

    /**
     * @param String $s
     * @return Integer
     */
    function firstUniqChar($s) {
        $words = str_split($s);
        $table = [];
        foreach($words as $word) {
            $table[$word] ??= 0;
            $table[$word]++;
        }

        $targets = array_filter($table, fn($item) => $item === 1);
        if (count($targets) === 0){
            return -1;
        }
        $keys = array_keys($targets);

        return array_search($keys[0], $words);
    }
}