Summary  
This chapter explains how to treat data from superglobals as unsafe by validating and sanitizing inputs to prevent injection attacks and by implementing session security measures (like regenerating session IDs and using secure cookies) to guard against session hijacking.

General domain of usage  
Web application security

When using PHP superglobals like `$_GET`, `$_POST`, `$_COOKIE`, and `$_SESSION`, you must treat all incoming data as unsafe. The main risks are **injection attacks** and **session hijacking**.

**Injection attacks** happen when unvalidated input is used in queries or commands, such as SQL injection. Always **validate and sanitize** user data before using it, especially in database operations or output.

**Session hijacking** occurs when attackers steal or guess session IDs. Protect sessions by regenerating session IDs after login, using `HttpOnly` and `Secure` cookies, and keeping session data out of URLs.

You should treat all superglobal data as untrusted. Never assume form, URL, cookie, or session values are safe or correctly formatted. Always validate the type, length, and format, and sanitize dangerous characters. This prevents injection, XSS, and other common attacks.

Note

By consistently applying these safe practices, you greatly reduce the risk of introducing security flaws into your PHP applications.

What is a recommended practice when working with user input from superglobals in PHP?

Learn the core PHP essentials needed to build dynamic, interactive web applications. Master functions, handle form data safely, work with superglobals, and manage file operations with confidence to create clean, secure, and reliable PHP projects.

Learn how to define, use, and manage functions in PHP, including parameters, return values, scope, and best practices.

Master the basics of handling web forms in PHP, including request methods, validation, and data processing.

Explore PHP's built-in superglobal variables for managing web data and sessions.

Gain practical skills in reading, writing, and uploading files securely in PHP.

Security Considerations with Superglobals