12. Associative Arrays in PHP

What is an associative array?

• An array indexed with numeric values

• An array indexed with strings called keys

• A graphical representation of data

• A database storage method

Answer explanation

Answer: An array indexed with strings called keys

Explanation: Associative arrays use character strings (keys) to describe the content of each element, unlike standard arrays that use numeric indices.

Which PHP function can be used to create associative arrays?

• array()

• new_array()

• create_array()

• set_array()

Answer explanation

Answer: array()

Explanation: The array() function, combined with the => operator, is used to create associative arrays in PHP.

What is a key characteristic of associative arrays?

• They only store numeric data

• They allow meaningful keys for elements

• They are always sorted alphabetically

• They are limited to database applications

Answer explanation

Answer: They allow meaningful keys for elements

Explanation: Associative arrays are useful when meaningful keys can be assigned to each array element.

Which array is automatically created when a form with the method “post” is submitted?

• $_SESSION

• $_REQUEST

• $_GET

• $_POST

Answer explanation

Answer: $_POST

Explanation: The $_POST array is populated with input field values submitted via a form using the “post” method.

What is the primary difference between $_GET and $_POST?

• $_GET is secure, $_POST is not

• $_GET includes data in the URL, while $_POST does not

• $_POST is read-only, $_GET is editable

• $_GET can handle larger data submissions than $_POST

Answer explanation

Answer: $_GET includes data in the URL, while $_POST does not

Explanation: The $_GET method sends data in the URL, making it less secure than $_POST.

What is the output of the following code snippet?

$userList['mike'] = "123";

echo $userList['mike'];

• An error

• "mike"

• 123

• null

Answer explanation

Answer: 123

Explanation: The associative array $userList stores “123” with the key 'mike'.

What happens when session_start() is called in PHP?

• A new session ID is created

• A session is resumed if one exists

• Session data becomes accessible

• All of the above

Answer explanation

Answer: All of the above

Explanation: The session_start() function initiates or resumes a session and makes session variables available.

How do you access a value in an associative array using a variable key?

• $array->$key

• $array($key)

• $array[$key]

• $array.$key

Answer explanation

Answer: $array[$key]

Explanation: Square brackets are used to access values in an associative array.

What does the isset() function do?

• Checks if a variable contains a value

• Checks if a variable exists

• Declares a variable

• Deletes a variable

Answer explanation

Answer: Checks if a variable exists

Explanation: The isset() function tests if a variable is defined and not null.

What is a use case for associative arrays?

• Storing ordered numerical data

• Replacing databases

• Implementing lookup tables

• Storing user sessions

Answer explanation

Answer: Implementing lookup tables

Explanation: Associative arrays are efficient for implementing lookups, where data is accessed via meaningful keys.