$_SERVER information in PHP

Introduction

The $_SERVER variable holds information about headers, paths, and script locations. It helps you learn about the current request and server environment.

To find out the user's IP address visiting your website.

To get the current page URL or script name.

To check which browser or device the visitor is using.

To know the server software or version running your site.

To handle redirects or links based on the current domain.

Syntax

PHP

$_SERVER['KEY_NAME'];

Replace KEY_NAME with the specific information you want, like REMOTE_ADDR for IP address.

$_SERVER is a superglobal array, so you can access it anywhere in your PHP script.

Examples

Prints the visitor's IP address.

PHP

echo $_SERVER['REMOTE_ADDR'];

Shows the browser or device details of the visitor.

PHP

echo $_SERVER['HTTP_USER_AGENT'];

Displays the path of the current script.

PHP

echo $_SERVER['SCRIPT_NAME'];

Sample Program

This program prints the visitor's IP, the current script path, and browser details using $_SERVER.

PHP

<?php
// Show some server info
echo "Your IP address is: " . $_SERVER['REMOTE_ADDR'] . "\n";
echo "You are visiting: " . $_SERVER['SCRIPT_NAME'] . "\n";
echo "Your browser info: " . $_SERVER['HTTP_USER_AGENT'] . "\n";
?>

Important Notes

Some $_SERVER keys may not be available depending on the server or request type.

Never trust $_SERVER data blindly; it can be spoofed by users.

Summary

$_SERVER holds useful info about the visitor and server.

You access it like an array with keys for different details.

It helps customize responses based on who visits and how.

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