Indexed array creation in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code creating an indexed array?

Consider the following PHP code that creates an indexed array. What will be the output when it is run?

PHP

<?php
$array = array('apple', 'banana', 'cherry');
print_r($array);
?>

A Array ( apple, banana, cherry )

B Array ( [0] => apple [1] => banana [2] => cherry )

C Array ( [0] => apple [2] => banana [4] => cherry )

D Array ( [1] => apple [2] => banana [3] => cherry )

💡 Hint

Remember that indexed arrays in PHP start with index 0 by default.

In PHP, when you create an indexed array without specifying keys, the indexes start at 0 and increase by 1 for each element. So the keys are 0, 1, and 2 for the three elements.

❓ Predict Output

intermediate

What is the output of this PHP code using short array syntax?

Look at this PHP code that uses the short array syntax. What will it output?

PHP

<?php
$fruits = ['orange', 'grape', 'melon'];
var_dump($fruits);
?>

A array(3) { [0]=> string(6) "orange" [1]=> string(5) "grape" [2]=> string(5) "melon" }

B Array ( [1] => orange [2] => grape [3] => melon )

C array(3) { [1]=> string(6) "orange" [2]=> string(5) "grape" [3]=> string(5) "melon" }

D Array ( orange, grape, melon )

💡 Hint

var_dump shows detailed info including indexes starting at zero.

The short array syntax [] creates an indexed array starting at 0. var_dump shows the type, length, and keys with values. So keys are 0,1,2 with corresponding strings.

❓ Predict Output

advanced

What is the output of this PHP code mixing keys and values in an indexed array?

What will this PHP code output when run?

PHP

<?php
$array = array(0 => 'zero', 2 => 'two', 'one');
print_r($array);
?>

A Array ( [0] => zero [1] => one [2] => two )

B Array ( [0] => zero [1] => two [2] => one )

C Array ( [0] => zero [2] => two [3] => one )

D Array ( [0] => zero [2] => two [1] => one )

💡 Hint

When mixing explicit keys and implicit values, PHP assigns the next index after the highest numeric key.

The array has keys 0 and 2 explicitly. The next value 'one' has no key, so PHP assigns it key 3 (one more than highest key 2).

❓ Predict Output

advanced

What error or output does this PHP code produce?

Examine this PHP code snippet. What will happen when it runs?

PHP

<?php
$array = array(1 => 'a', 3 => 'b', 2 => 'c');
print_r($array);
?>

A Array ( [1] => a [3] => b [2] => c )

B Array ( [0] => a [1] => b [2] => c )

C SyntaxError: Unexpected token

D Array ( [1] => a [2] => c [3] => b )

💡 Hint

PHP arrays can have keys in any order; print_r shows them in insertion order.

The array keys are explicitly set as 1, 3, and 2. PHP keeps keys as given. print_r outputs them in the order inserted.

🧠 Conceptual

expert

How many elements are in this PHP indexed array after execution?

After running this PHP code, how many elements does the array contain?

PHP

<?php
$array = [];
$array[] = 'first';
$array[5] = 'sixth';
$array[] = 'seventh';
?>

A 2

B 5

C 4

D 3

💡 Hint

Appending without key uses the highest existing numeric key plus one.

Initially empty array. First append adds element at index 0. Then index 5 is set. Next append adds element at index 6 (5 + 1). So total elements: 3.