In PHP, what is the use of superglobal arrays and why are they important for accessing request, server, and session data?

Introduction / Context:
When writing PHP web applications, scripts need to access information about form inputs, query strings, cookies, sessions, server variables, and file uploads. PHP provides a set of predefined arrays known as superglobals that make this data available everywhere in a script without extra plumbing. This question checks whether you understand what superglobal arrays are used for and why they are central to PHP web programming.

Given Data / Assumptions:

• PHP runs requests in a stateless HTTP environment where each request has its own data.
• Input data can arrive via GET parameters, POST bodies, cookies, and file uploads.
• Server and environment information is also needed for logging, debugging, and routing.
• Developers want a consistent way to access this information in any function or method.

Concept / Approach:
Superglobal arrays such as $_GET, $_POST, $_REQUEST, $_COOKIE, $_SESSION, $_FILES, $_SERVER, and $_ENV are special because they are available in all scopes automatically. You do not need to declare them as global inside functions. Each superglobal has a specific role, such as holding query parameters, posted form data, or session state. Together they represent the interface between PHP and the request or environment. Using these arrays correctly ensures that an application can read user inputs, manage sessions, and react to server context in a secure and predictable way.

Step-by-Step Solution:
Step 1: Recall that superglobal arrays are predefined by PHP and have names that start with an underscore and uppercase letters.Step 2: Understand that their main use is to store and expose request and environment data, such as $_GET for query parameters and $_POST for form fields.Step 3: Note that $_SESSION stores user specific data on the server side across requests, while $_COOKIE contains cookie values sent by the browser.Step 4: Recognise that $_SERVER and $_ENV provide information about the server environment, script paths, and other context.Step 5: Conclude that the big advantage of superglobals is their automatic availability in all scopes, which simplifies access to global request and environment data.

Verification / Alternative check:
You can verify the behaviour of superglobals by writing a simple PHP script that prints their contents inside a function and in the global scope. Even without using the global keyword, the arrays will contain the same data inside the function. This confirms that they are truly global across scopes. Documentation and examples in PHP manuals consistently show superglobals as the primary way to access HTTP and server related data, reinforcing their role and importance.

Why Other Options Are Wrong:
Option B says that superglobal arrays automatically compress file uploads, which is not true; file uploads are represented in $_FILES and compression is not automatic. Option C claims they are the only arrays that store numeric values, which is false because any PHP array can hold numbers and other types. Option D restricts them to command line use, but superglobals are especially important in web requests, not limited to the command line interface. These statements do not match the real purpose of superglobals.

Common Pitfalls:
A common pitfall is relying heavily on $_REQUEST, which merges GET, POST, and COOKIE data and can lead to confusion or security issues. It is better to use the specific superglobal that matches the expected source of data. Another mistake is assuming that superglobals are automatically sanitised; developers still need to validate and escape input values to prevent attacks such as SQL injection or cross site scripting. Understanding the role and limitations of superglobals helps you write clearer and safer PHP code.

Final Answer:
Correct answer: They are built in arrays available in all scopes that provide access to request, server, session, and other global data