How to use PHP to implement WeChat applet login function

WeChat is currently one of the instant messaging software with the largest number of users in the world, and WeChat mini programs occupy a significant market share among mobile applications. How to implement the login and authentication functions of WeChat mini programs is a skill that many developers are concerned about and need to master. In this article, we will use PHP as the back-end language to explain how to use the API and SDK officially provided by WeChat to implement the login function of the WeChat applet.

1. WeChat Mini Program login process

Before introducing how to use PHP to implement the WeChat Mini Program login function, we first need to understand the WeChat Mini Program login process.

1. The user opens the WeChat applet and clicks the login button.
2. The WeChat client pops up an authorization window, requesting user authorization to log in.
3. The user clicks the Confirm Authorization button in the authorization window.
4. The WeChat client uses the authorization temporary ticket (code) to send a request to the WeChat server in exchange for the user's openid and session_key.
5. The WeChat server returns the user's openid and session_key to the client, and these sensitive information will be saved on the client for one hour.
6. The applet generates the user's unique identity credential (session_id) based on the obtained openid and session_key, and stores it on the applet server or a third-party server.
7. When the user has been authorized, the applet uses session_id to authenticate the user's identity.

2. WeChat Mini Program Login SDK Application

To use the WeChat Mini Program login function, we need to apply for the corresponding API interface and SDK first. The application process is as follows:

1. Find the WeChat open platform (https://open.weixin.qq.com/) and log in with a WeChat enterprise account.
2. Enter [Management Center]-[Development]-[Developer Center]
3. Click [Add Project], fill in the relevant information of the mini program, and check [Mini Program Login], select "PHP" language type, after submission, two keys, AppID and AppSecret, will be generated. These two keys are used for subsequent interface and SDK calls.
4. Download the corresponding SDK, decompress it and copy the files to the project for use.
5. PHP code implementation

After applying for the API interface and SDK, we can use PHP to implement the login function of the WeChat applet. The specific implementation steps are as follows:

1. Read the code sent by the WeChat client and send it to the WeChat server to obtain the user openid and session_key.

$code = $_GET['code'];
$url = "https://api.weixin.qq.com/sns/jscode2session?appid=" . $appid . "&secret=" . $appsecret . "&js_code=" . $code . "&grant_type=authorization_code";
$res = json_decode(file_get_contents($url), true);
$openid = $res['openid'];
$session_key = $res['session_key'];

2. Use the obtained openid and session_key to generate the user's unique identity credential, and store the credential in a database or third-party server.

$session_id = md5(uniqid(mt_rand(), true));
$redis->set($session_id, json_encode(array('openid'=>$openid, 'session_key'=>$session_key)), 3600); //存储一个小时

3. Send the generated session_id to the applet client for user authentication.

echo json_encode(array('session_id'=>$session_id));

4. Confirm whether the user's identity is valid based on session_id.

$session_id = $_POST['session_id'];
$userinfo = json_decode($redis->get($session_id), true);
if($userinfo){
    $openid = $userinfo['openid'];
    //验证身份成功，进行其他查询或操作
}else{
    //验证身份失败，提示用户重新授权登录
}

The above is the basic process and code example for using PHP to implement the WeChat applet login function. Of course, this is just a simple example, and the specific implementation needs to be optimized and adjusted according to your actual needs.

4. Summary

Through the above explanation of the WeChat applet login process, SDK application and PHP code implementation, I believe that readers have a certain understanding and mastery. Login and authentication of WeChat mini programs are essential skills for many developers. In actual development, issues such as security, performance and experience need to be taken into consideration. At the same time, it is also necessary to pay attention to WeChat official development documents and the latest developments, and update and optimize applications in a timely manner. program.

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