$_REQUEST behavior in PHP

Introduction

$_REQUEST lets you get data sent by a user through forms or URLs in one simple place.

When you want to get data from a form that can use GET or POST methods.

When you want to read query parameters from a URL or form inputs without checking each method separately.

When you want a quick way to access user input without worrying about where it came from.

When you want to handle both cookies and form data in one place (if configured).

Syntax

PHP

$_REQUEST['key']

$_REQUEST is a PHP superglobal array that contains data from $_GET, $_POST, and $_COOKIE.

The order of data in $_REQUEST depends on the PHP configuration setting request_order or variables_order.

Examples

This code gets the 'name' value from any request method and prints a greeting.

PHP

<?php
// Access a value sent by GET, POST, or COOKIE
$name = $_REQUEST['name'];
echo "Hello, $name!";
?>

This checks if 'age' was sent and prints it or a message if not.

PHP

<?php
// Check if a value exists in $_REQUEST
if (isset($_REQUEST['age'])) {
    echo "Age is " . $_REQUEST['age'];
} else {
    echo "Age not provided.";
}
?>

Sample Program

This program demonstrates that manually assigning values to $_GET, $_POST, and $_COOKIE inside the script does not populate $_REQUEST, as $_REQUEST is assembled from incoming HTTP request data before the script executes. In real scenarios, $_REQUEST prioritizes based on request_order (typically 'GP', so GET then POST).

PHP

<?php
// Simulate GET and POST data
$_GET['color'] = 'blue';
$_POST['color'] = 'red';
$_COOKIE['color'] = 'green';

// By default, request_order is usually 'GP' meaning GET then POST
// But let's print what $_REQUEST['color'] gives

echo "Color from $_REQUEST: " . $_REQUEST['color'] . "\n";

// To show the difference, print each superglobal
echo "Color from $_GET: " . $_GET['color'] . "\n";
echo "Color from $_POST: " . $_POST['color'] . "\n";
echo "Color from $_COOKIE: " . $_COOKIE['color'] . "\n";
?>

Important Notes

$_REQUEST can be slower and less secure because it mixes data sources.

It's better to use $_GET, $_POST, or $_COOKIE directly when you know where data should come from.

Check your PHP request_order setting to understand which data $_REQUEST uses first.

Summary

$_REQUEST combines GET, POST, and COOKIE data into one array.

It is easy to use but can cause confusion if you don't know the data source order.

Use it for quick access, but prefer specific superglobals for clarity and security.

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