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11 questions to solve
Instructions
- This quiz goes to full-screen once you press the Start button.
- At the end of the quiz, you are able to review all the questions that you answered wrong and see their explanations.
Identify the error in the code below:
<?php
$a = [1, 2, 3];
$a[3] = 'Hello';There's absolutely no error in the code shown. Hence, the correct choice is (C). For more info, refer to PHP Arrays — Basics — Adding elements.
What is the value of
$a after the execution of the following code?<?php
$a = [1, 2, 3];
$a[] = 4;The statement
$a[] = 4 adds the value 4 to the end of the array $a. This makes $a equal to [1, 2, 3, 4]. Hence, the correct choice is (C). For more info, refer to PHP Arrays — Basics — Adding elements.What does the following code output?
<?php
$a = [];
array_push($a, [1, 2]);
print_r($a);array_push($a, [1, 2]) adds the array [1, 2] to the end of $a. The output of $a therefore resembles the one shown in choice (C). For more info, refer to PHP Arrays — Basics — Adding elements.Which of the following can be used to remove the last element from an array
$arr?We're not concerned with removing the element in a way such that the subsequent addition of an element happens on the correct index.
array_pop() is an answer for sure, hence the choice (A). Talking about unset($arr[count($arr) - 1]), the question's description clearly states that we're not concerned with such a removal that a subsequent addition of element gets done on the correct index; likewise choice (E) is also correct. For more info, refer to PHP Arrays — Basics — Removing elements.Determine the length of
$arr after the following code executes:<?php
$arr = [1, 0];
unset($arr[0]);unset($arr[0]) removes the key 0 from $arr. Consequently, the length of $arr becomes 1. Thus, the correct choice is (A). For more info, refer to PHP Arrays — Basics — Removing elements.An indexed array in PHP is technically also an associative array. True or false?
That's absolutely true. Indexed arrays in PHP are also associative arrays — their keys are simply indexes while the corresponding values are the elements of the indexed arrays. For more info, refer to PHP Arrays — Basics — Associative arrays.
What does the following code output?
<?php
$a = [1, 2];
print_r(array_keys($a));array_keys($a) returns an indexed array containing all the keys of $a. This gives us [0, 1]. The output that resembles this array is the one in choice (A). For more info, refer to PHP Arrays — Basics — array_keys().Determine the value of
$c after the following code executes:<?php
$a = [1, 2];
$b = [3, 4];
$c = $a + $b;$a + $b performs the union of $a and $b based on their keys, with the keys of $a overriding those of $b. This gives us [1, 2]. Hence, the correct choice is (A). For more info, refer to PHP Arrays — Basics — Array operators.What does
[1] === [1] return?[1] === [1] returns true since the identity operator (===) compares two arrays based on the individual key-value pairs they contain (in this case, both [1] and [1] contain the same key-value pairs). For more info, refer to PHP Arrays — Basics — Array operators.What does the following code output?
<?php
$a = [10, 20];
var_dump(in_array(true, $a));Surprisingly enough,
in_array(true, $a) returns true. That's because in_array(), by default, compares the given value with each array element loosely, i.e. using the semantics of the equality (==) operator, and true == 10 is a truthy expression! For more info, refer to PHP Arrays — Basics — Searching elements.What does the following code output?
<?php
$nums = [-5, 1];
var_dump(array_search(true, $nums));
var_dump(array_search(true, $nums, true));The first
Hence, the correct choice is (D). For more info, refer to PHP Arrays — Basics — Searching elements.
array_search() call indeed finds true in $nums in the number -5, by virtue of loose comparisons, and returns 0. The second array_search() call, however, doesn't find a match for true in $nums, by virtue of strict comparisons (enabled by the third true argument), and returns false.Hence, the correct choice is (D). For more info, refer to PHP Arrays — Basics — Searching elements.
