$_REQUEST behavior in PHP - Mini Project: Build & Apply

Understanding $_REQUEST Behavior in PHP

📖 Scenario: You are building a simple PHP script that collects user input from different sources: URL parameters, form data sent via POST, and cookies. You want to understand how PHP's $_REQUEST superglobal works by combining these inputs.

🎯 Goal: Create a PHP script that sets up sample $_GET, $_POST, and $_COOKIE data, then uses $_REQUEST to access all these values together. Finally, display the combined results.

📋 What You'll Learn

Create arrays for $_GET, $_POST, and $_COOKIE with exact keys and values

Create a variable request_order that defines the order of $_REQUEST variables

Use $_REQUEST to combine all inputs according to request_order

Print the combined $_REQUEST array

💡 Why This Matters

🌍 Real World

Web developers often need to handle user input from multiple sources like URL parameters, form submissions, and cookies. Understanding $_REQUEST helps manage these inputs safely and predictably.

💼 Career

Knowing how to work with PHP superglobals like $_REQUEST is essential for backend web development, especially when building forms, handling sessions, and processing user data.

1

Setup $_GET, $_POST, and $_COOKIE arrays

Create the PHP arrays $_GET, $_POST, and $_COOKIE with these exact entries:
$_GET = ['color' => 'red', 'size' => 'large'];
$_POST = ['color' => 'blue', 'shape' => 'circle'];
$_COOKIE = ['size' => 'medium', 'texture' => 'smooth'];

PHP

<?php

// Create the $_GET, $_POST, and $_COOKIE arrays with exact entries
// Your code here

Hint

Use PHP array syntax to assign the exact keys and values to $_GET, $_POST, and $_COOKIE.

2

Define request_order variable

Create a variable called request_order and set it to the string 'GP' to specify that $_REQUEST should prioritize $_GET then $_POST variables.

PHP

 'red', 'size' => 'large'];
$_POST = ['color' => 'blue', 'shape' => 'circle'];
$_COOKIE = ['size' => 'medium', 'texture' => 'smooth'];

// Create the variable $request_order with value 'GP'
// Your code here

Hint

Assign the string 'GP' to the variable $request_order.

3

Combine arrays into $_REQUEST according to request_order

Create the $_REQUEST array by combining $_GET, $_POST, and $_COOKIE according to the order in $request_order. Use array_merge in the order of $_GET then $_POST then $_COOKIE.

PHP

 'red', 'size' => 'large'];
$_POST = ['color' => 'blue', 'shape' => 'circle'];
$_COOKIE = ['size' => 'medium', 'texture' => 'smooth'];

$request_order = 'GP';

// Combine $_GET, $_POST, and $_COOKIE into $_REQUEST according to $request_order
// Your code here

Hint

Use array_merge($_COOKIE, $_POST, $_GET) to combine the arrays in the order specified by $request_order.

4

Print the combined $_REQUEST array

Use print_r to display the contents of the $_REQUEST array.

PHP

 'red', 'size' => 'large'];
$_POST = ['color' => 'blue', 'shape' => 'circle'];
$_COOKIE = ['size' => 'medium', 'texture' => 'smooth'];

$request_order = 'GP';

$_REQUEST = array_merge($_COOKIE, $_POST, $_GET);

// Print the $_REQUEST array
// Your code here

Hint

Use print_r($_REQUEST); to show the combined array.

Practice

1. What does the PHP superglobal $_REQUEST contain?

easy

A. Data from GET, POST, and COOKIE combined

B. Only data sent via GET method

C. Only data sent via POST method

D. Only data stored in cookies

Solution

1. Step 1: Understand the purpose of $_REQUEST

   $_REQUEST is designed to collect data from multiple sources: GET, POST, and COOKIE.

2. Step 2: Identify what $_REQUEST includes

   It merges these three superglobals into one array for easier access.

3. Final Answer:

   Data from GET, POST, and COOKIE combined -> Option A

4. Quick Check:

   $_REQUEST = GET + POST + COOKIE [OK]

Hint: Remember: $_REQUEST mixes GET, POST, and COOKIE data [OK]

Common Mistakes:

• Thinking $_REQUEST only contains GET or POST data
• Confusing $_REQUEST with $_POST or $_GET
• Assuming $_REQUEST excludes cookies

2. Which of the following is the correct way to access a form field named username using $_REQUEST in PHP?

easy

A. $_REQUEST->username

B. request['username']

C. $_REQUEST.username

D. $_REQUEST['username']

Solution

1. Step 1: Recall PHP array syntax

   PHP superglobals like $_REQUEST are associative arrays accessed with square brackets and quotes for keys.

2. Step 2: Identify correct syntax for accessing 'username'

   The correct syntax is $_REQUEST['username']. Using arrows or dots is invalid for arrays.

3. Final Answer:

   $_REQUEST['username'] -> Option D

4. Quick Check:

   Array access uses brackets and quotes [OK]

Hint: Use square brackets with quotes for $_REQUEST keys [OK]

Common Mistakes:

• Using object notation (->) instead of array syntax
• Using dot notation like in JavaScript
• Forgetting quotes around the key

3. Given the following PHP code, what will be the output if the URL is script.php?color=red and the form sends color=blue via POST?

<?php
print_r($_REQUEST['color']);
?>

medium

A. red

B. Array

C. blue

D. Undefined index error

Solution

1. Step 1: Understand the order of variables in $_REQUEST

   By default, PHP's $_REQUEST uses the order: GET, POST, COOKIE. POST data overrides GET if keys are the same.

2. Step 2: Determine which value $_REQUEST['color'] holds

   Since POST sends color=blue, it overrides the GET color=red. So, $_REQUEST['color'] is 'blue'.

3. Final Answer:

   blue -> Option C

4. Quick Check:

   POST overrides GET in $_REQUEST [OK]

Hint: POST data overrides GET in $_REQUEST by default [OK]

Common Mistakes:

• Assuming GET value appears first
• Confusing $_REQUEST with $_GET or $_POST
• Expecting an array output

4. Consider this PHP snippet:

<?php
print_r($_REQUEST['user']);
?>

If the form sends no 'user' field and the URL has no 'user' parameter, what error will occur and how to fix it?

medium

A. No error; prints empty string

B. Notice: Undefined index; fix by checking with isset()

C. Warning: Invalid argument; fix by casting to string

D. Fatal error: Undefined variable; fix by declaring variable

Solution

1. Step 1: Identify the error from accessing missing key

   Accessing $_REQUEST['user'] when 'user' is not set causes a Notice: Undefined index.

2. Step 2: Fix by checking if key exists

   Use isset($_REQUEST['user']) before accessing to avoid the notice.

3. Final Answer:

   Notice: Undefined index; fix by checking with isset() -> Option B

4. Quick Check:

   Check keys with isset() to avoid notices [OK]

Hint: Always check isset() before accessing $_REQUEST keys [OK]

Common Mistakes:

• Ignoring undefined index notices
• Confusing undefined index with undefined variable
• Assuming no error occurs when key missing

5. You want to safely get a user's preferred language from either GET, POST, or COOKIE using $_REQUEST, but prefer POST over GET and GET over COOKIE. Which code snippet correctly respects this priority?

hard

A. if(isset($_POST['lang'])) { $lang = $_POST['lang']; } elseif(isset($_GET['lang'])) { $lang = $_GET['lang']; } elseif(isset($_COOKIE['lang'])) { $lang = $_COOKIE['lang']; } else { $lang = 'en'; }

B. $lang = $_REQUEST['lang'] ?? 'en';

C. $lang = $_COOKIE['lang'] ?? $_GET['lang'] ?? $_POST['lang'] ?? 'en';

D. $lang = $_GET['lang'] ?? $_POST['lang'] ?? $_COOKIE['lang'] ?? 'en';

Solution

1. Step 1: Understand priority order requirement

   The priority is POST > GET > COOKIE, so check in that order.

2. Step 2: Analyze each option's order

   if(isset($_POST['lang'])) { $lang = $_POST['lang']; } elseif(isset($_GET['lang'])) { $lang = $_GET['lang']; } elseif(isset($_COOKIE['lang'])) { $lang = $_COOKIE['lang']; } else { $lang = 'en'; } checks POST first, then GET, then COOKIE, assigning default 'en' if none set. $lang = $_REQUEST['lang'] ?? 'en'; uses $_REQUEST which merges but order depends on php.ini and is less explicit. Options C and D check in wrong orders.

3. Final Answer:

   Option A code snippet -> Option A

4. Quick Check:

   Explicit checks respect priority best [OK]

Hint: Check POST, then GET, then COOKIE explicitly for priority [OK]

Common Mistakes:

• Relying on $_REQUEST without knowing order
• Checking keys in wrong priority order
• Not providing a default value