In PHP, what are the purposes of the superglobal arrays $_SERVER and $_ENV when handling web requests?

Introduction / Context:
Among the PHP superglobal variables, $_SERVER and $_ENV give scripts insight into the environment in which they are running. They are frequently used for tasks such as building URLs, logging client information, and reading configuration from environment variables. This question focuses on the specific roles of these two arrays so that you can distinguish between server context information and operating system level environment variables in a PHP application.

Given Data / Assumptions:

• PHP is running in a web server or command line environment where server and environment data is available.
• $_SERVER and $_ENV are predefined superglobal arrays that can be accessed from any scope.
• Scripts may need information such as the current script name, request method, or environment flags.
• The goal is to understand what each array typically contains.

Concept / Approach:
$_SERVER is populated by the web server or SAPI layer and usually contains details of the HTTP request and script environment. Typical keys include SERVER_NAME, REQUEST_METHOD, REQUEST_URI, HTTP_USER_AGENT, and SCRIPT_FILENAME. These values describe the client request, the host, and the script path. $_ENV, on the other hand, contains environment variables passed from the operating system or server configuration, such as PATH, HOME, or application specific variables. While the exact contents vary by server and configuration, the conceptual difference is that $_SERVER is about the request and server context, whereas $_ENV is about the broader environment variables available to the process.

Step-by-Step Solution:
Step 1: Recall that $_SERVER is filled with request and server related information such as host name, protocol, script paths, and HTTP headers.Step 2: Recognise that $_ENV is used to expose environment variables from the operating system or shell into the PHP script.Step 3: Understand that both arrays are superglobals, so they are available in any function without needing a global declaration.Step 4: Consider practical usage, such as using $_SERVER["REQUEST_URI"] to know which URL was requested or $_ENV["APP_ENV"] to check the current deployment environment.Step 5: Confirm that the correct description is that $_SERVER deals with headers, paths, and request context, while $_ENV exposes environment variables.

Verification / Alternative check:
You can verify the difference by writing a small script that prints out $_SERVER and $_ENV with print_r. On a typical web server, $_SERVER will contain many HTTP related keys, while $_ENV will have values similar to those seen when running the env command in a shell. If your hosting environment disables $_ENV for security reasons, it may be empty, which further highlights that its content depends on how the environment variables are passed to PHP.

Why Other Options Are Wrong:
Option B incorrectly claims that $_SERVER stores session variables and $_ENV stores cookies. Session data is held in $_SESSION and cookies in $_COOKIE. Option C suggests that $_SERVER holds database connection parameters and $_ENV contains form fields, which is not the standard behaviour because database settings are usually in configuration files and form fields are stored in $_POST or $_GET. Option D assigns $_SERVER only to command line scripts and $_ENV only to graphical interfaces, which does not reflect how PHP superglobals are defined and populated.

Common Pitfalls:
A common pitfall is assuming that values from $_SERVER and $_ENV are always trustworthy. Many of these values can be influenced by client requests or by server configuration, so they should be validated and sanitised before use in logging, redirects, or security decisions. Another mistake is relying on non portable keys that exist only in specific server software. Writing code that checks for the presence of keys and falls back gracefully helps keep applications portable and secure.

Final Answer:
Correct answer: $_SERVER contains information about headers, paths, and script environment, while $_ENV exposes environment variables from the operating system