PHP Detect if non-english

Try this (please note you need mbstring php module installed):

<?php
    $string="で書くタッチイベント (フ";

    if(strlen($string) != mb_strlen($string, 'utf-8'))
    { 
        echo "Please enter English words only:(";
    }
    else {
        echo "OK, English Detected!";
    }
?>