How to avoid php super global variable errors

In PHP, superglobal variables refer to global variables that can be used anywhere in the script. These variables do not need to be declared to be used, they are predefined and already initialized by PHP.

Common PHP superglobal variables include $_GET, $_POST, $_COOKIE, $_SESSION, $_SERVER, etc.

The advantage of using super global variables is that you can easily obtain the data submitted by the form, the user's browser information, etc. However, some problems may occur during use, such as:

• Undefined variable: If you try to use an undefined superglobal variable, an Undefined variable error will be thrown.
• Variable is empty: If a superglobal variable does not receive any data, it will be empty, and using this variable will also cause an error.
• Variables are tampered with: When submitting form data, an attacker can tamper with super-global variables, causing security vulnerabilities in the program.

In order to avoid super-global variable errors, we can take the following measures:

1. Perform variable checking

Before using a super-global variable , first check if it has been defined and is not empty. This can be achieved through the isset() and empty() functions.

For example, the following code can check whether the $_GET variable contains a parameter named "id":

if(isset($_GET['id']) && !empty($_GET['id'])) {
    // 处理 $_GET['id'] 变量
}

2. Perform data filtering

In When using superglobal variables, you must remember not to pass unfiltered data directly into the database or other sensitive operations, otherwise security issues such as SQL injection may occur. You can use PHP's built-in filter functions, such as addslashes(), htmlentities(), etc.

For example, the following code can filter the $_POST variable using the addslashes() function:

$username = addslashes($_POST['username']);
$password = addslashes($_POST['password']);

3. Using HTTPS protocol

If the superglobal variable is used To transfer sensitive information, it is recommended to use HTTPS protocol for encrypted transmission to solve the problem of data tampering or theft. You can do this by configuring your website to use an SSL/TLS certificate.

4. Enable strict mode

PHP 7 introduced a new feature called strict mode (strict_types). After enabling strict mode, PHP will check data types more strictly, reducing bugs caused by type conversion errors. Strict mode can be enabled by adding the following code to the head of the PHP file:

declare(strict_types=1);

In short, when using PHP superglobal variables, be sure to pay attention to security and consistency. Perform rigorous data filtering and validation, and follow best practices to protect program and user data.

The above is the detailed content of How to avoid php super global variable errors. For more information, please follow other related articles on the PHP Chinese website!