PHP calculate string length

/**
* Calculate the length of the string (Chinese characters are calculated as two characters)
*
* @param string $str String
*
* @return int
*/
function myStrLen($str){
    $length = strlen(preg_replace('/[x00-x7F]/', '', $str));

    if ($length){
        return strlen($str) - $length + intval($length / 3) * 2;
    }
    else{
        return strlen($str);
    }
}

/**
* Calculate the length of the string (Chinese characters are calculated as one character)
*
* @param string $str String
*
* @return int
*/
function cnForOneBetLen($str){
    $length = strlen(preg_replace('/[x00-x7F]/', '', $str));

    if ($length){
        return strlen($str) - $length + intval($length / 3) * 1;
    }
    else{
        return strlen($str);
    }
}