How to nest php scripts in javascript-Front-end Q&A-php.cn

JavaScript is a widely used programming language, while PHP is a scripting language used on the server side. In the process of web development, we often need to combine these two languages. This article will introduce you in detail how to embed PHP scripts in JavaScript and what you need to pay attention to.

1. Why do we need to embed PHP scripts in JavaScript?

In web development, we often need to dynamically update the content of the page based on the user's behavior, such as real-time calculation based on the data input by the user. results, or dynamically display different content based on the options selected by the user. These functions usually require the use of JavaScript.

On the server side, we often use PHP to handle the generation and output of dynamic data. For example, after a user submits form data, we need to send the data to the server, process it using PHP, and finally return the processed results to the user. In this way, we need to embed PHP scripts in JavaScript to achieve the purpose of data interaction between the server and the client.

2. Use ajax technology to achieve nesting

The most common way to nest PHP scripts in JavaScript is to use Ajax technology.

Ajax is a set of technologies for creating asynchronous web applications that can send asynchronous requests and update parts of a page without refreshing the entire page. Usually, we write Ajax code in the JavaScript of the page, use JavaScript to send the request to the server, the server will return the processed data, and finally we use JavaScript to update the data to the page.

When using Ajax technology, you need to create an XMLHttpRequest object first, and then use this object to send a request to the server. The following is a typical Ajax code:

var xhr = new XMLHttpRequest();
xhr.open('POST', 'example.php', true);
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
xhr.onload = function () {
  //处理返回的数据
};
xhr.send('data=value');

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In this code, we first create an XMLHttpRequest object and specify the request method (POST), target URL and whether it is asynchronous through the open method. Then, we set the request header through the setRequestHeader method to tell the server that the requested data type is application/x-www-form-urlencoded. Next, we process the data returned from the server in the onload method. Finally, we use the send method to send a request to the server and set the data data to value.

In PHP scripts, we can use the $_POST array to obtain the data submitted by the client. The following is a simple PHP example:

<?php
$data = $_POST['data'];
$result = doSomethingWithData($data);
echo $result;
?>

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In this example, we first use the $_POST array to obtain the data submitted by the client, and then use the doSomethingWithData function to process the data and output the result.

3. Handling of cross-domain requests

When using Ajax technology, we need to pay attention to one issue, that is, the limitations of cross-domain requests. A cross-domain request refers to a request that sends a request to another domain name or port, such as sending a request from http://example.com to http://localhost:8080.

Restrictions on cross-domain requests are implemented by the browser. By default, the browser does not allow cross-domain requests and will output a similar error message to the console:

Access to XMLHttpRequest at 'http://localhost:8080/example.php' from origin 'http://example.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

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To solve the limitations of cross-domain requests, we can add CORS (Cross-Origin Resource Sharing) on the server side ) header information, add the Access-Control-Allow-Origin header to the response, and set the domain name list that allows cross-domain requests. In PHP, you can add CORS headers in the following way:

header('Access-Control-Allow-Origin: http://example.com');

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The above code will allow cross-origin requests from http://example.com.

In addition to adding CORS headers, we can also use JSONP (JSON with Padding) to implement cross-domain requests. JSONP is a technology that utilizes the characteristics of the