php5.4以下版本json不支持不转义内容中文的解决方法

        if ($var === true)
            return 'true';

        if ($var === false)
            return 'false';

        static $reps = array(
            array("\\", "/", "\n", "\t", "\r", "\b", "\f", '"', ),
            array('\\\\', '\\/', '\\n', '\\t', '\\r', '\\b', '\\f', '\"', ),
        );

        if (is_scalar($var))
            return '"' . str_replace($reps[0], $reps[1], (string) $var) . '"';

        if (!is_array($var))
            throw new Exception('JSON encoder error!');

        $isMap = false;
        $i = 0;
        foreach (array_keys($var) as $k) {
            if (!is_int($k) || $i++ != $k) {
                $isMap = true;
                break;
            }
        }

        $s = array();

        if ($isMap) {
            foreach ($var as $k => $v)
                $s[] = '"' . $k . '":' . call_user_func(__FUNCTION__, $v);

            return '{' . implode(',', $s) . '}';
        } else {
            foreach ($var as $v)
                $s[] = call_user_func(__FUNCTION__, $v);

            return '[' . implode(',', $s) . ']';
        }
    }
}