Array access and modification in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

How do you access the first element of an array in PHP?

Use the index 0 inside square brackets after the array variable. For example: $array[0] accesses the first element.

beginner

How do you change the value of an element in a PHP array?

Assign a new value to the element using its index or key. For example: $array[2] = 'new value'; changes the third element.

intermediate

What happens if you assign a value to an array index that does not exist yet?

PHP will add a new element at that index with the assigned value. This can create new elements dynamically.

beginner

How do you add a new element to the end of an array without specifying an index?

Use empty square brackets to append: $array[] = 'new element'; adds the element at the end.

beginner

How do you access an element in an associative array by key?

Use the key inside square brackets as a string. For example: $array['key'] accesses the element with that key.

What does $array[1] return in PHP?

A The first element of the array

B The second element of the array

C The last element of the array

D An error

Array indexes start at 0, so index 1 is the second element.

How do you add a new element to the end of an array without specifying the index?

A Both A and C

B $array[] = 'value';

C array_push($array, 'value');

D $array[0] = 'value';

Both $array[] = 'value'; and array_push($array, 'value'); add elements to the end.

What happens if you assign a value to $array[5] when the array has only 3 elements?

A PHP adds a new element at index 5

B PHP throws an error

C PHP replaces the third element

D PHP ignores the assignment

PHP creates a new element at index 5, leaving indexes 3 and 4 undefined.

How do you access the value associated with the key 'name' in an associative array?

A $array.name

B $array[name]

C $array->name

D $array['name']

Keys in associative arrays must be in quotes inside square brackets.

Which of the following is the correct way to change the third element of an array to 10?

A $array(2) = 10;

B $array[3] = 10;

C $array[2] = 10;

D $array->2 = 10;

Arrays start at index 0, so the third element is at index 2.

Explain how to access and modify elements in a PHP array.

Think about how you use square brackets with the array variable.

Describe what happens when you assign a value to an array index that does not exist yet in PHP.

PHP arrays are flexible and can grow as you assign new indexes.