$_SERVER information in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the $_SERVER variable in PHP?

$_SERVER is a superglobal array in PHP that contains information about headers, paths, and script locations. It provides details about the server environment and the current request.

beginner

What does $_SERVER['REQUEST_METHOD'] represent?

It shows the HTTP method used to access the page, such as GET or POST. This tells you how the user sent data to the server.

intermediate

Explain $_SERVER['HTTP_USER_AGENT'].

This contains information about the user's browser or client software. It helps identify what device or browser the visitor is using.

beginner

What information does $_SERVER['SERVER_NAME'] provide?

It gives the name of the server host that is running the script, usually the domain name or IP address.

intermediate

How can $_SERVER['SCRIPT_FILENAME'] be useful?

It shows the full path and filename of the currently executing script. This helps when you need to know exactly where your PHP file is located on the server.

Which $_SERVER key contains the IP address of the client?

A SERVER_ADDR

B HTTP_USER_AGENT

C REMOTE_ADDR

D SERVER_NAME

REMOTE_ADDR holds the IP address of the user visiting the page.

What does $_SERVER['REQUEST_URI'] represent?

A The client's browser type

B The full URL of the current page

C The server's root directory

D The URI which was given to access the page

REQUEST_URI is the URI (path and query) used to access the page, like /index.php?name=John.

Which $_SERVER key tells you the HTTP method used (GET, POST, etc.)?

A HTTP_METHOD

B REQUEST_METHOD

C METHOD_TYPE

D SERVER_METHOD

REQUEST_METHOD contains the HTTP method used for the request.

If you want to know the name of the script currently running, which $_SERVER key do you use?

A SCRIPT_NAME

B SCRIPT_FILENAME

C PHP_SELF

D SERVER_NAME

SCRIPT_NAME gives the path of the current script relative to the root, like /folder/script.php.

What does $_SERVER['HTTP_REFERER'] contain?

A The URL of the previous page that linked to the current page

B The IP address of the server

C The user's browser language

D The server software version

HTTP_REFERER shows the URL of the page that sent the user to the current page, if available.

Describe what kind of information you can get from the $_SERVER array in PHP and why it might be useful.

Think about what the server and browser tell your PHP script during a request.

Explain how you would use $_SERVER['REQUEST_METHOD'] in a PHP script that handles form submissions.

Consider how forms send data and how your script knows when to act.

Practice

1. What type of data does the PHP $_SERVER superglobal array hold?

easy

A. User input from forms

B. Information about headers, paths, and script locations

C. Database connection details

D. Session variables

Solution

1. Step 1: Understand what $_SERVER contains

   $_SERVER holds server and execution environment information like headers and script paths.

2. Step 2: Compare with other options

   User input is in $_POST or $_GET, database details are not stored here, and session variables are in $_SESSION.

3. Final Answer:

   Information about headers, paths, and script locations -> Option B

4. Quick Check:

   $_SERVER = server info [OK]

Hint: Remember: $_SERVER = server and request info [OK]

Common Mistakes:

• Confusing $_SERVER with $_POST or $_GET
• Thinking $_SERVER holds user session data
• Assuming $_SERVER contains database info

2. Which of the following is the correct way to get the current script's filename using $_SERVER?

easy

A. $_SERVER['SCRIPT_NAME']

B. $_SERVER['USER_AGENT']

C. $_SERVER['REMOTE_ADDR']

D. $_SERVER['HTTP_HOST']

Solution

1. Step 1: Identify the key for current script filename

   $_SERVER['SCRIPT_NAME'] returns the path of the current script.

2. Step 2: Understand other keys

   USER_AGENT is client browser info, REMOTE_ADDR is client IP, and HTTP_HOST is the host name.

3. Final Answer:

   $_SERVER['SCRIPT_NAME'] -> Option A

4. Quick Check:

   Script filename = $_SERVER['SCRIPT_NAME'] [OK]

Hint: SCRIPT_NAME gives current script path [OK]

Common Mistakes:

• Using REMOTE_ADDR for filename
• Confusing HTTP_HOST with script name
• Trying USER_AGENT for script info

3. What will the following PHP code output if the visitor's IP address is 192.168.1.10?

echo $_SERVER['REMOTE_ADDR'];

medium

A. 192.168.1.10

B. The server's IP address

C. The visitor's browser name

D. An empty string

Solution

1. Step 1: Understand what REMOTE_ADDR holds

   $_SERVER['REMOTE_ADDR'] contains the IP address of the client visiting the page.

2. Step 2: Match with given IP

   The visitor's IP is 192.168.1.10, so that is what will be printed.

3. Final Answer:

   192.168.1.10 -> Option A

4. Quick Check:

   REMOTE_ADDR = visitor IP [OK]

Hint: REMOTE_ADDR shows visitor IP address [OK]

Common Mistakes:

• Thinking REMOTE_ADDR is server IP
• Confusing REMOTE_ADDR with HTTP_USER_AGENT
• Expecting browser name instead of IP

4. Identify the error in this PHP code snippet that tries to print the visitor's browser info:

echo $_SERVER[HTTP_USER_AGENT];

medium

A. $_SERVER cannot be echoed directly

B. Using wrong key name

C. Missing quotes around the array key

D. HTTP_USER_AGENT is not available in $_SERVER

Solution

1. Step 1: Check array key syntax

   Array keys must be strings in quotes. Here, HTTP_USER_AGENT is missing quotes.

2. Step 2: Confirm key existence

   HTTP_USER_AGENT is a valid key in $_SERVER, so the key name is correct.

3. Final Answer:

   Missing quotes around the array key -> Option C

4. Quick Check:

   Array keys need quotes [OK]

Hint: Always quote $_SERVER keys like 'HTTP_USER_AGENT' [OK]

Common Mistakes:

• Forgetting quotes around keys
• Assuming key name is wrong
• Trying to echo whole $_SERVER array directly

5. You want to create a PHP script that shows the visitor's IP address and the current script's filename. Which code snippet correctly does this?

hard

A. echo 'IP: ' . $_SERVER['REMOTE_HOST'] . ', Script: ' . $_SERVER['SCRIPT_FILENAME'];

B. echo 'IP: ' . $_SERVER['SCRIPT_NAME'] . ', Script: ' . $_SERVER['REMOTE_ADDR'];

C. echo 'IP: ' . $_SERVER['HTTP_HOST'] . ', Script: ' . $_SERVER['REMOTE_ADDR'];

D. echo 'IP: ' . $_SERVER['REMOTE_ADDR'] . ', Script: ' . $_SERVER['SCRIPT_NAME'];

Solution

1. Step 1: Identify keys for IP and script filename

   REMOTE_ADDR is visitor IP, SCRIPT_NAME is current script path.

2. Step 2: Check code correctness

   echo 'IP: ' . $_SERVER['REMOTE_ADDR'] . ', Script: ' . $_SERVER['SCRIPT_NAME'];

   correctly concatenates IP and script name.

   echo 'IP: ' . $_SERVER['SCRIPT_NAME'] . ', Script: ' . $_SERVER['REMOTE_ADDR'];

   swaps them incorrectly.

   echo 'IP: ' . $_SERVER['HTTP_HOST'] . ', Script: ' . $_SERVER['REMOTE_ADDR'];

   uses HTTP_HOST (server host) instead of IP.

   echo 'IP: ' . $_SERVER['REMOTE_HOST'] . ', Script: ' . $_SERVER['SCRIPT_FILENAME'];

   uses REMOTE_HOST (often empty) and SCRIPT_FILENAME (full path, not filename).

3. Final Answer:

   echo 'IP: ' . $_SERVER['REMOTE_ADDR'] . ', Script: ' . $_SERVER['SCRIPT_NAME']; -> Option D

4. Quick Check:

   IP = REMOTE_ADDR, Script = SCRIPT_NAME [OK]

Hint: Use REMOTE_ADDR for IP and SCRIPT_NAME for script path [OK]

Common Mistakes:

• Mixing up REMOTE_ADDR and SCRIPT_NAME
• Using HTTP_HOST instead of REMOTE_ADDR
• Using REMOTE_HOST which may be empty