Leetcode PHP题解--D81 520. Détecter le capital

<?php
class Solution {    /**
     * @param String $word
     * @return Boolean
     */
    function detectCapitalUse($word) {
        $wordArray = str_split($word);
        $uppercase = str_split(&#39;ABCDEFGHIJKLMNOPQRSTUVWXYZ&#39;);
        $lowercase = str_split(&#39;abcdefghijklmnopqrstuvwxyz&#39;);       
        //all upper or lower case
        if(!array_diff_key(array_count_values($wordArray),array_flip($uppercase))
           ||!array_diff_key(array_count_values($wordArray),array_flip($lowercase))){            return true;
        }        //first letter whatever case,
        //rest of the string must be all lowercase
        array_shift($wordArray);        if(!array_diff_key(array_count_values($wordArray),array_flip($lowercase))){           return true; 
        }        return false;
    }
}