中文字符问题,PHP webservice

I am calling one webservice which developed in the php. the response of WS is not being correct while i select Chinese language. for other language its fine but for Chinese behavior is abnormal.

the output of WS is

{

    "response": {
        "@attributes": {
            "error": 0
        },
        "code": 200,
        "message": "success",
        "data": [
            {
                "faq_id": "4",
                "app_id": "7",
                "question": "What is the main goal for the conference?",
                "answer": "This conference is designed to review our Q3 achievements and plan our Q4 goals",
                "status": "1"
            },
            {
                "faq_id": "5",
                "app_id": "7",
                "question": "??????????????",
                "answer": "This is strictly an employee only conference.",
                "status": "1"
            },
            {
                "faq_id": "6",
                "app_id": "7",
                "question": "Where do we stay for the conference?",
                "answer": "Details on accomodations will be provided to you before the conference begins",
                "status": "1"
            }
        ]
    }

}  

and i am expecting "question":"我们可以得到我们的家庭会议?" instead of "question": "??????????????",

please help me to sort out this issue. thanks in advance.

Try this simple code:

EDIT

    $str1 = base64_encode("我们可以得到我们的家庭会议?");
    $str2 = base64_decode($str1);
    echo $str2;

This gives the characters as they are. So, while sending the data to web service (from database) for question encode it and decode it again. Because the problem is with encoding for these characters.