PHP根据IP地址获取所在城市具体实现(2)

/**
     * 判断是否我utf-8编码的字符串
     * @param type $string
     * @return boolean
     */
    private function is_utf8( $string ) {
        if ( preg_match( "/^([" . chr( 228 ) . "-" . chr( 233 ) . "]{1}[" . chr( 128 ) . "-" . chr( 191 ) . "]{1}[" . chr( 128 ) . "-" . chr( 191 ) . "]{1}){1}/", $string ) == true || preg_match( "/([" . chr( 228 ) . "-" . chr( 233 ) . "]{1}[" . chr( 128 ) . "-" . chr( 191 ) . "]{1}[" . chr( 128 ) . "-" . chr( 191 ) . "]{1}){1}$/", $string ) == true || preg_match( "/([" . chr( 228 ) . "-" . chr( 233 ) . "]{1}[" . chr( 128 ) . "-" . chr( 191 ) . "]{1}[" . chr( 128 ) . "-" . chr( 191 ) . "]{1}){2,}/", $string ) == true ) {
            return true;
        } else {
            return false;
        }
    }

}