PHP communication: How to achieve cross-domain data transmission?

PHP communication: How to achieve cross-domain data transmission?

Introduction:
In web development, it is often necessary to realize data transmission between different domain names, which requires cross-domain communication. This article will introduce how to use PHP language to achieve cross-domain data transmission, and attach code examples.

1. What is cross-domain communication?
Cross-domain communication refers to the process of data transmission between different domain names in web development. Typically, browsers prevent pages from sending requests or receiving responses to servers in different domains due to limitations of the same-origin policy. Therefore, in order to achieve data communication between different domains, we need to find a way to bypass the restrictions of the same origin policy.

2. Cross-domain communication method

1. JSONP: By dynamically creating <script> tags in the page, cross-domain data transmission is achieved. The server needs to return a piece of JS code that executes the specified callback function, so that the page can obtain the data and process it. </script>
2. CORS: Cross-domain resource sharing is a standard cross-domain communication method that allows pages in different domains to send cross-domain requests through relevant configurations on the server side. The server needs to return specific response header information to indicate whether cross-domain access is allowed.
3. iframe window.postMessage: Communicate by embedding
4. Proxy method: Make a data request on the server side of the same source page, and then return the data to the client. The client obtains data by accessing the same origin server, thereby bypassing cross-domain issues.

3. Use PHP to implement JSONP cross-domain communication
JSONP is a simple cross-domain communication method, which is more suitable for simple data transmission. The following is an example:

<?php
// 获取传入的回调函数名
$callback = $_GET['callback'];

// 需要返回的数据
$data = ['name' => 'John', 'age' => 25];

// 返回JSONP格式的数据
echo $callback . '(' . json_encode($data) . ')';
?>

In the above code, first obtain the incoming callback function name through $_GET['callback']. Then, construct the data that needs to be returned and use the json_encode() function to convert the data into JSON format. Finally, the callback function name and JSON data are concatenated and output.

In the client code, make a request by creating a <script> tag on the page and setting the src attribute to achieve cross-domain data acquisition. For example: </script>

<script>
function handleData(data) {
    console.log(data);
}

var script = document.createElement('script');
script.src = 'http://example.com/api.php?callback=handleData';
document.getElementsByTagName('head')[0].appendChild(script);
</script>

In the above code, create the <script> tag and set the src attribute to the URL of the API, and pass in the callback function name handleData. When the server returns data, the callback function is automatically executed and the data is passed in as a parameter, thereby achieving cross-domain data acquisition. </script>

Conclusion:
By using different cross-domain communication methods, we can achieve data transmission between different domains in web development. This article introduces the method of using JSONP to achieve cross-domain communication in PHP and provides corresponding code examples. In actual development, appropriate cross-domain communication methods are selected according to needs so that data can be transferred and processed between different domains.

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