How to clear passed value in php? Common situation sharing

PHP is now the most popular server-side language, but in use, we sometimes need to clear or reset the passed values ​​to avoid some unexpected or wrong results. This article will explain how to clear passed values ​​in PHP and provide some common scenarios for clearing values.

What is the value passed?

In PHP, the value passed refers to the data stored in the super global variable. Super global variables are a special type of variables that can be used in any scope, including within functions, outside functions, within classes, and outside classes. Some common super global variables include $_GET, $_POST, $_COOKIE, $_SESSION, etc.

Super global variables are sent to the server through HTTP requests. For example, when you submit data through a form, the data is passed to the server as part of an HTTP GET or POST request sent from the browser. The server parses the request using PHP and stores the passed values ​​in super global variables so they can be used in scripts.

You may need to clear or reset the passed value when necessary. Here are some situations where you might want to do this:

1. Prevent Cross-Site Scripting Attacks (XSS)

XSS attack is a type of attack that occurs by injecting malicious scripts into a web application techniques to attack users. An attacker can inject JavaScript code into the user's browser to force the execution of any code. For PHP websites, the frequently used passing parameters have proven to be a common attack method.

2. Avoid using inappropriate values

Sometimes, you may receive an error or incorrect value. In this case, you need to disable or clear the passed value to avoid incorrect or wrong results.

3. Clear cache

If you are using cache, you need to clear the passed value if necessary. Otherwise, you may encounter old or incorrect data displayed on cached web pages.

How to clear the passed value

There are two ways to clear the passed value. The first method is to use the unset() function. The unset() function deletes the defined variable. For example:

unset($_GET['id']);

In this example, we use the unset() function to delete the "id" variable in the $_GET array. After the run, the variable is no longer available and its value has been deleted.

The second method is to set the passed value to NULL. For example:

$_GET['id'] = NULL;

In this example, we set the "id" variable in the $_GET array to NULL. After running, the value of $_GET['id'] will not have a variable, but the variable will still exist.

There should not be a significant performance difference between using the unset() function and setting the variable to NULL. However, in the case of using the unset() function, you need to ensure that the variable is defined. Otherwise, you will encounter a "Variable not found" error.

Clear super global variables

In addition to using the unset() function and setting the variable to NULL, you can also use super global variables to clear the passed value.

For example, if you want to delete all keys and values ​​in the $_POST, $_GET, $_COOKIE and $_SESSION arrays, you can use the following code:

$_POST = array();
$_GET = array();
$_COOKIE = array();
$_SESSION = array();

After running, all super globals All values ​​in the variable array will be cleared.

Also, using super global variables will make it easier for you to handle the passed values ​​in your code. For example, you can use the following method to check if the $_POST['submit'] variable exists:

if(isset($_POST['submit'])){
     // 在这里添加您的代码
}

In this example, we use an if statement to check if the key named "submit" exists in the $_POST array . If present, the code will be executed.

Conclusion

Clearing passed values ​​may be the key to making your PHP website more secure, reliable and stable. Whether it's preventing cross-site scripting attacks or avoiding the use of inappropriate values, clearing passed values ​​can be a big help. You can easily clear passed values ​​and make your PHP scripts more robust by using the unset() function, setting variables to NULL, or using a superglobal array.

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