How to implement cross-domain request processing in PHP back-end function development?

How to implement cross-domain request processing in PHP back-end function development?

Concept explanation:
Cross-domain request refers to the situation where requests are made between different domain names, different ports or different protocols. Due to the browser's security mechanism, cross-domain requests will be restricted and may result in request failure or loss of relevant data. In order to solve this problem, we need to handle cross-domain requests in PHP back-end development.

1. Understand the restrictions on cross-domain requests
Before processing cross-domain requests, you first need to understand the browser's restrictions on cross-domain requests. The limitations of cross-domain requests mainly include the following aspects:

1. Different domain names: the source and target of the request must be the same domain name, such as http://www.example.com and http://api .example.com cannot make cross-domain requests.
2. Different ports: The source and target of the request must be the same port. For example, http://www.example.com and http://www.example.com:8080 cannot make cross-domain requests.
3. Different protocols: The source and target of the request must be the same protocol. For example, https://www.example.com and http://www.example.com cannot make cross-domain requests.
4. Request header restrictions: Certain request header information (such as Cookie, Authorization, etc.) requires special processing before being sent in cross-domain requests.

2. Methods of handling cross-domain requests

1. CORS (Cross-domain Resource Sharing)
   CORS is a cross-domain solution standardized by W3C. It You can enable the server to support cross-domain requests and add relevant information to the response headers.

The method to implement CORS in PHP is as follows:

header('Access-Control-Allow-Origin: *');  // 允许所有域名访问
header('Access-Control-Allow-Headers: X-Requested-With,Content-Type,Accept,Origin');  // 允许特定请求头
header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE');  // 允许特定请求方法

// 处理跨域请求
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
    header('HTTP/1.1 204 No Content');
    exit;
}

By setting Access-Control-Allow-Origin, Access-Control- Response headers such as Allow-Headers and Access-Control-Allow-Methods can support cross-domain requests. In the request header, you can set Origin to specify the cross-domain domain names that are allowed, or you can use the wildcard character * to allow all domain names.

2. JSONP (JSON with Padding)
   JSONP is a method that uses the <script> tag to implement cross-domain requests. In the PHP backend, cross-domain requests are implemented by dynamically generating a JavaScript function call and returning it to the front end.

The method of implementing JSONP in PHP is as follows:

$data = ['name' => 'example'];
$callback = $_GET['callback'];  // 获取回调函数名

$jsonp = $callback . '(' . json_encode($data) . ')';  // 将数据转为JSONP格式

header('Content-Type: text/javascript');
echo $jsonp;

By dynamically generating a callback function and returning it, the PHP backend can respond to cross-domain requests.

3. Summary
In the development of PHP back-end functions, if you need to handle cross-domain requests, you can achieve it through methods such as CORS or JSONP. By setting response header information or dynamically generating callback function calls and returning data, you can solve the problem of cross-domain requests. Based on specific needs and scenarios, choose an appropriate method to handle cross-domain requests and ensure the security of cross-domain requests.

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