$_GET for URL parameters in PHP - Mini Project: Build & Apply

Using $_GET to Read URL Parameters in PHP

📖 Scenario: You are building a simple PHP page that greets users by their name passed in the URL.

🎯 Goal: Create a PHP script that reads a name parameter from the URL using $_GET and displays a greeting message.

📋 What You'll Learn

Create a PHP variable to store the name parameter from $_GET

Set a default value if the name parameter is not provided

Display a greeting message using the name variable

💡 Why This Matters

🌍 Real World

Reading URL parameters is common in web pages to customize content based on user input or links.

💼 Career

Understanding how to use <code>$_GET</code> is essential for PHP web developers to handle user requests and build dynamic websites.

1

Create a PHP variable to get the name parameter from the URL

Write a line of PHP code to create a variable called name that gets the value from $_GET['name'].

PHP

Hint

Use $name = $_GET['name']; to get the URL parameter.

2

Add a default value if name is not set in the URL

Add a line of PHP code to set $name to "Guest" if $_GET['name'] is not set or empty.

PHP

Hint

Use empty() to check if $name has no value and assign "Guest" if true.

3

Create a greeting message using the name variable

Write a line of PHP code to create a variable called greeting that stores the string "Hello, " followed by the value of $name.

PHP

Hint

Use the dot . operator to join strings in PHP.

4

Display the greeting message

Write a line of PHP code to print the $greeting variable.

PHP

Hint

Use print($greeting); to show the message on the page.

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