Sort Special Words

sortWords.php

<?php
function sortWords(String $string){

    $words = explode(' ', $string);
    $numWords = count($words);
    $englishWords = [];
    $chineseWords = [];

    for($i=0; $i<$numWords; $i++){
        if(ctype_alnum($words[$i])){
            if(!in_array($words[$i], $englishWords, true)) {
                array_push($englishWords, $words[$i]);
            }
        }else{
            array_push($chineseWords, $words[$i]);
        }
    }
    return implode(' ', $englishWords) . ' ' . implode(' ', array_reverse($chineseWords));
}