$_GET for URL parameters in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code using $_GET?

Consider the URL: http://example.com/page.php?name=Alice&age=30. What will this PHP code output?

PHP

<?php
$name = $_GET['name'];
$age = $_GET['age'];
echo "Name: $name, Age: $age";
?>

A Name: , Age: 30

B Name: Alice, Age: 30

C Name: Alice, Age:

D Name: , Age:

💡 Hint

Check how $_GET accesses URL parameters by their keys.

The $_GET superglobal array contains URL parameters as key-value pairs. Accessing $_GET['name'] returns 'Alice' and $_GET['age'] returns '30'.

🧠 Conceptual

intermediate

What happens if a URL parameter is missing in $_GET?

Given the URL http://example.com/page.php?user=Bob, what will be the output of this code?

PHP

<?php
$user = $_GET['user'];
$age = $_GET['age'];
echo "User: $user, Age: $age";
?>

A User: Bob, Age: 0

B User: Bob, Age: NULL

C User: Bob, Age:

D User: Bob, Age: Notice: Undefined index: age

💡 Hint

Accessing a missing key in $_GET causes a notice error.

Trying to access $_GET['age'] when 'age' is not in the URL causes a PHP Notice: Undefined index error.

🔧 Debug

advanced

Why does this PHP code not output the expected $_GET value?

URL: http://example.com/page.php?city=Paris Code:

<?php
$city = $_GET[city];
echo "City: $city";
?>

What is the problem?

A Missing quotes around 'city' key causes a PHP notice or error.

B The $_GET array is empty because URL parameters are not passed.

C The variable $city is overwritten before echo.

D The echo statement syntax is incorrect.

💡 Hint

Array keys must be quoted strings in PHP.

In PHP, array keys must be quoted strings. Using $_GET[city] without quotes causes PHP to look for a constant named city, which is undefined and triggers a notice.

❓ Predict Output

advanced

What is the output of this PHP code with multiple $_GET parameters?

URL: http://example.com/page.php?item=book&price=15&discount=5 Code:

<?php
$item = $_GET['item'];
$price = $_GET['price'];
$discount = $_GET['discount'];
$total = $price - $discount;
echo "Item: $item, Total Price: $total";
?>

A Item: book, Total Price: 20

B Item: book, Total Price: 15-5

C Item: book, Total Price: 10

D Item: book, Total Price: 0

💡 Hint

URL parameters are strings; PHP converts them to numbers in arithmetic.

PHP converts string numbers to integers automatically in arithmetic operations. 15 - 5 equals 10.

📝 Syntax

expert

Which option causes a syntax error when accessing $_GET parameters?

Identify the code snippet that will cause a PHP syntax error.

A $value = $_GET['key']

B $value = $_GET[key];

C $value = $_GET["key"];

D $value = $_GET['key'];

💡 Hint

Check for missing semicolons in PHP statements.

Option A is missing the semicolon at the end of the statement, causing a syntax error.

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