Associative array creation in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an associative array in PHP?

An associative array in PHP is a collection of key-value pairs where each key is a unique string or integer used to access its corresponding value.

beginner

How do you create an associative array with keys 'name' and 'age' in PHP?

You create it like this:<br>$person = ['name' => 'Alice', 'age' => 30];<br>This means 'name' points to 'Alice' and 'age' points to 30.

intermediate

What happens if you use the same key twice in an associative array?

The last value assigned to that key will overwrite any previous value. Keys must be unique in an associative array.

beginner

How can you access the value of the key 'age' in an associative array named $person?

Use the syntax: $person['age']; This will give you the value stored under the key 'age'.

beginner

Can keys in PHP associative arrays be integers?

Yes, keys can be integers or strings. PHP treats integer keys as normal keys in associative arrays.

Which of the following is the correct way to create an associative array in PHP?

A $arr = array('red', 'large');

B $arr = ('color', 'red', 'size', 'large');

C $arr = ['red', 'large'];

D $arr = ['color' => 'red', 'size' => 'large'];

Option D uses the correct syntax with keys and values. Options A, B, and C do not create associative arrays with keys.

What will be the output of echo $arr['name']; if $arr = ['name' => 'Bob'];?

A Bob

B name

C Error

D Array

Accessing $arr['name'] returns the value 'Bob' stored under the key 'name'.

If you create $arr = ['key' => 'first', 'key' => 'second'];, what is the value of $arr['key']?

A first

B second

C Array

D Error

The second value overwrites the first for the same key, so $arr['key'] is 'second'.

Which data types can be used as keys in PHP associative arrays?

A Only strings

B Only integers

C Strings and integers

D Any data type

PHP allows keys to be strings or integers in associative arrays.

How do you add a new key-value pair 'city' => 'Paris' to an existing associative array $arr?

A $arr['city'] = 'Paris';

B $arr->city = 'Paris';

C array_push($arr, 'city' => 'Paris');

D $arr.add('city', 'Paris');

You add a new key-value pair by assigning it directly: $arr['city'] = 'Paris';

Explain how to create and access values in an associative array in PHP.

Think about how you label things with names and then find them by those names.

Describe what happens if you use duplicate keys when creating an associative array.

Imagine writing a label twice on the same box.