$GLOBALS in PHP

Summary

In this tutorial, Durgesh Sahni introduces PHP's super global variables, explaining how they are used to access form values across different pages. He covers key super globals like `$_GET`, `$_POST`, `$_SERVER`, `$_COOKIE`, and `$_SESSION`, demonstrating how they function in PHP to retrieve and manipulate data. The video also includes practical examples, such as accessing and modifying variable scopes with the `global` keyword and understanding variable access within functions. By the end of the tutorial, viewers will grasp the foundational concepts of super global variables and their usage in PHP development.

Takeaways

• 😀 Super Global Variables in PHP allow access to values across different forms and scopes in a stateless protocol like HTTP.
• 😀 The 'GET' and 'POST' methods are commonly used for passing values between forms in PHP, with 'GET' being the default method.
• 😀 To access form values using the 'GET' or 'POST' method, PHP provides the super global variables $_GET and $_POST.
• 😀 The $_SERVER super global provides access to server-related information, which can be accessed with the '$_SERVER' variable.
• 😀 Cookies and sessions in PHP can be accessed and managed using their respective super global variables: $_COOKIE and $_SESSION.
• 😀 PHP functions may require the use of the 'global' keyword to access variables outside the function's scope.
• 😀 Variables declared outside a function may not be directly accessible inside it unless the 'global' keyword is used.
• 😀 Using the '$GLOBALS' super global allows access to any global variable from anywhere within the script, including inside functions.
• 😀 PHP functions have local scopes, meaning variables declared within them cannot be accessed outside unless explicitly returned or handled by super global variables.
• 😀 To access a global variable inside a function, one must use '$GLOBALS' or declare the variable as 'global' within the function.
• 😀 The scope of a PHP variable determines its accessibility. Variables outside the function cannot be accessed directly unless specified using super global variables.

Q & A

What are super global variables in PHP?

Super global variables in PHP are built-in global arrays that are accessible from any part of the script, including inside functions. They are used to collect data from forms, server variables, cookies, and sessions.

Why do we need super global variables in PHP?

Super global variables are essential because they allow data to be accessed globally throughout a PHP script, making it possible to retrieve and manipulate information from different sources like forms, URLs, and server settings.

What is the difference between $_GET and $_POST methods in PHP?

The `$_GET` method is used to collect form data sent via the URL (query string), while `$_POST` is used to collect form data sent through HTTP POST, which is more secure as the data is not visible in the URL.

How does PHP handle variable scope with respect to super global variables?

Super global variables in PHP are accessible from anywhere in the script, including inside functions, without needing to pass them explicitly. However, other non-super global variables are only accessible within their defined scope.

What error occurs when trying to access a non-global variable inside a function in PHP?

If a non-global variable is accessed inside a function without declaring it as global, PHP will throw an 'undefined variable' error, as the variable is out of the function's scope.

How can we access a global variable inside a PHP function?

To access a global variable inside a PHP function, you need to use the `global` keyword followed by the variable name or access it using the `GLOBALS` array.

What is the purpose of the `$_SERVER` super global in PHP?

The `$_SERVER` super global contains information about headers, paths, and script locations. It can be used to get details like the server's hostname, script name, or request method.

What happens if a global variable is not declared inside a function when using the `global` keyword?

If a global variable is not declared inside the function using the `global` keyword, PHP will not be able to access it, resulting in an 'undefined variable' error.

What is the role of the `$_COOKIE` and `$_SESSION` super globals?

The `$_COOKIE` super global is used to retrieve values from cookies set on the user's browser, while the `$_SESSION` super global is used to store session data across page requests.

How can a variable be accessed globally if it is declared inside a function?

If a variable is declared inside a function and you want to access it globally, you can use the `global` keyword or store it in the `GLOBALS` array to make it available outside the function.