PHP cannot get the parameter value passed by ajax

To solve the problem that PHP cannot obtain the parameter values ​​​​from Ajax, you must have an in-depth understanding of Ajax technology, PHP language and web development. This article will help you solve this problem by analyzing the Ajax parameter passing process and PHP's implementation of Ajax parameter value acquisition.

Ajax technology is a front-end web development technology that can communicate with the server without reloading the page and can update page content asynchronously. Ajax can be implemented through languages ​​such as jQuery and JavaScript. PHP is a back-end programming language used to handle server-side logic and business and render dynamic data into front-end pages.

When sending an Ajax request in the front-end page, we can pass parameter values ​​in the request through the data attribute, as shown below:

$.ajax({
  url: "example.php",
  method: "POST",
  data: {"name": "张三", "age": "20"},
  success: function(response) {
    console.log(response);
  }
});

Here we pass two parameter values, respectively "name" and "age". In PHP code, we can use the $_POST superglobal variable to obtain the parameter value passed by Ajax, as shown below:

<?php
$name = $_POST["name"];
$age = $_POST["age"];

echo "姓名：" .$name. "，年龄：" .$age;
?>

However, sometimes we encounter PHP being unable to obtain the parameter value passed by Ajax. Case. This may be due to the following reasons:

1. The content-type is not set correctly

When sending an Ajax request, we need to set the content-type to "application/json" or "application/x-www-form-urlencoded" to ensure that the transmitted data is in the correct format. If the content-type is set incorrectly, PHP will not parse the parameter value correctly.

2. Errors in parameter names and parameter values

If the parameter names or parameter values ​​in the data transmitted by Ajax are incorrect, PHP will not be able to parse the data correctly. We need to make sure that the parameter names and parameter values ​​are in the correct format and consistent with the variable names in the PHP code behind the scenes.

3. Incorrect request method

Ajax requests can use the GET or POST method. If you use $_POST in PHP code to get data, and the actual request sent uses the GET method, PHP will not be able to get the data.

To address these problems, we can have the following solutions:

1. Set the correct content-type

If you are using JSON format data, The content-type should be set to "application/json". If form data is being transmitted, it should be set to "application/x-www-form-urlencoded". For example:

//设置请求头为 application/json
$.ajax({
  url: "example.php",
  method: "POST",
  contentType:"application/json;charset=utf-8",
  data: JSON.stringify({"name": "张三", "age": "20"}),
  success: function(response) {
    console.log(response);
  }
});

//设置请求头为 application/x-www-form-urlencoded
$.ajax({
  url: "example.php",
  method: "POST",
  contentType:"application/x-www-form-urlencoded;charset=utf-8",
  data: {"name": "张三", "age": "20"},
  success: function(response) {
    console.log(response);
  }
});

2. Confirm whether the parameter name and parameter value are correct

Before sending the Ajax request, we should carefully check the format of the parameter name and parameter value to ensure that they are consistent with the background code The variable names in are consistent. If the parameter name or parameter value is incorrect, PHP will not be able to parse the data.

3. Confirm whether the request method is correct

In the PHP code, we use $_POST to obtain the data transmitted by the POST request. If the request method is GET, we should use $_GET to get the transferred data. At the same time, we can also use $_REQUEST to obtain data regardless of the request method.

In short, if PHP cannot obtain the parameter value sent by Ajax, you must carefully check the above issues, find the problem and make corresponding solutions.

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