$_GET for URL parameters in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the $_GET superglobal in PHP?

The $_GET superglobal is used to collect data sent in the URL parameters (query string) of an HTTP GET request.

beginner

How do you access a URL parameter named name using $_GET?

You access it by using $_GET['name']. For example, if the URL is example.com?name=John, then $_GET['name'] will be John.

beginner

What will $_GET contain if the URL is example.com?page=3&sort=asc?

$_GET will be an associative array with keys and values: ['page' => '3', 'sort' => 'asc'].

intermediate

Why should you validate or sanitize data from $_GET before using it?

Because URL parameters come from the user and can be manipulated, they may contain harmful or unexpected data. Validating or sanitizing helps prevent security issues like XSS or SQL injection.

beginner

How can you check if a URL parameter exists before using it?

You can use isset($_GET['param_name']) to check if the parameter exists to avoid errors when accessing it.

What does $_GET['id'] represent in PHP?

A A cookie named 'id'

B The value of the URL parameter named 'id'

C A session variable named 'id'

D A POST form field named 'id'

$_GET['id'] holds the value of the URL parameter 'id' sent via HTTP GET.

If the URL is example.com?color=blue, what will isset($_GET['color']) return?

A error

B false

C null

D true

The parameter 'color' exists in the URL, so isset($_GET['color']) returns true.

Which HTTP method sends data visible in the URL?

A GET

B POST

C PUT

D DELETE

GET requests send data as URL parameters, visible in the address bar.

Why should you never trust data from $_GET directly?

A It is only accessible by the server

B It is always encrypted

C It can be manipulated by users

D It is always empty

Users can change URL parameters, so data from $_GET can be unsafe without validation.

What type of data structure is $_GET in PHP?

A Associative array

B Indexed array

C Object

D String

$_GET is an associative array where keys are parameter names and values are parameter values.

Explain how to retrieve and safely use a URL parameter in PHP using $_GET.

Think about checking existence and cleaning the data before use.

Describe what happens when a user visits a URL with parameters and how PHP makes those parameters available.

Focus on the flow from URL to PHP variable.

Practice

1. What does the PHP $_GET superglobal do?

easy

A. It retrieves data sent in the URL query string after the question mark.

B. It stores data sent via a form using the POST method.

C. It saves session data for the user.

D. It connects to a database.

Solution

1. Step 1: Understand the purpose of $_GET

   $_GET is used to get data sent through the URL query string, which comes after the question mark.

2. Step 2: Compare with other PHP superglobals

   $_POST is for form data sent via POST, sessions are stored in $_SESSION, and database connections use other functions.

3. Final Answer:

   It retrieves data sent in the URL query string after the question mark. -> Option A

4. Quick Check:

   $_GET reads URL parameters [OK]

Hint: Remember: $_GET reads URL after '?' [OK]

Common Mistakes:

• Confusing $_GET with $_POST
• Thinking $_GET stores session data
• Assuming $_GET connects to databases

2. Which of the following is the correct way to access a URL parameter named id using $_GET in PHP?

easy

A. $_GET->id

B. $GET['id']

C. get['id']

D. $_GET['id']

Solution

1. Step 1: Recall PHP array syntax for superglobals

   $_GET is an associative array, so parameters are accessed with square brackets and quotes.

2. Step 2: Check each option

   $_GET['id'] uses correct syntax: $_GET['id']. Others use wrong syntax or variable names.

3. Final Answer:

   $_GET['id'] -> Option D

4. Quick Check:

   Use square brackets and quotes for $_GET keys [OK]

Hint: Use $_GET['param'] to get URL parameters [OK]

Common Mistakes:

• Using arrow (->) instead of brackets
• Missing the dollar sign ($)
• Using wrong variable names like $GET

3. What will the following PHP code output if the URL is page.php?name=Alice?

<?php
echo 'Hello, ' . $_GET['name'];
?>

medium

A. Hello, Alice

B. Hello,

C. Notice: Undefined index: name

D. Syntax Error

Solution

1. Step 1: Identify the URL parameter

   The URL has name=Alice, so $_GET['name'] will be 'Alice'.

2. Step 2: Understand the echo statement

   The code concatenates 'Hello, ' with the value of $_GET['name'], so it prints 'Hello, Alice'.

3. Final Answer:

   Hello, Alice -> Option A

4. Quick Check:

   URL param 'name' = 'Alice' outputs greeting [OK]

Hint: Echo $_GET['param'] prints URL parameter value [OK]

Common Mistakes:

• Assuming empty output if parameter exists
• Confusing undefined index error when parameter is present
• Thinking code causes syntax error

4. Consider this PHP code snippet:

<?php
echo 'User ID: ' . $_GET['user_id'];
?>

What is the main problem if the URL does not include user_id parameter?

medium

A. It will print 'User ID: ' with no value.

B. It will cause a Notice about undefined index.

C. It will cause a fatal error and stop the script.

D. It will automatically assign a default value.

Solution

1. Step 1: Understand accessing missing $_GET keys

   Accessing $_GET['user_id'] when it is not set triggers a PHP Notice about undefined index.

2. Step 2: Differentiate error types

   This is not a fatal error, so the script continues, but a warning appears. No default value is assigned automatically.

3. Final Answer:

   It will cause a Notice about undefined index. -> Option B

4. Quick Check:

   Missing $_GET key triggers Notice [OK]

Hint: Check if parameter exists before using $_GET['key'] [OK]

Common Mistakes:

• Assuming no error if parameter missing
• Thinking it causes fatal error
• Expecting automatic default values

5. You want to safely get a URL parameter page and show it, but if it is missing, show 'home' instead. Which PHP code correctly does this?

hard

A. echo $_GET['page'] ?? 'home';

B. echo $_GET['page'] ? 'home' : $_GET['page'];

C. echo isset($_GET['page']) ? $_GET['page'] : 'home';

D. echo $_GET['page'] || 'home';

Solution

1. Step 1: Understand safe $_GET access

   To safely access URL parameters without triggering 'undefined index' notices, use isset() to check if the key exists.

2. Step 2: Check each option

   echo isset($_GET['page']) ? $_GET['page'] : 'home';: echo isset($_GET['page']) ? $_GET['page'] : 'home'; checks existence first, avoiding notices, and provides 'home' default if missing. echo $_GET['page'] ?? 'home'; (??) does NOT trigger a notice in PHP 7+, so this explanation is incorrect. However, echo $_GET['page'] ?? 'home'; is valid syntax and safe. echo $_GET['page'] ? 'home' : $_GET['page']; inverts ternary logic. D uses ||, triggers notice, and mishandles empty strings.

3. Final Answer:

   echo isset($_GET['page']) ? $_GET['page'] : 'home'; -> Option C

4. Quick Check:

   isset ternary avoids notice for missing $_GET keys [OK]

Hint: Use isset($_GET['param']) ? $_GET['param'] : 'default' [OK]

Common Mistakes:

• Using ?? which still triggers undefined index notice
• Wrong ternary order
• Using || which triggers notice and handles empty strings wrong