PHP Array Interview Questions and Answers

PHP array is a special type of variable that stores multiple values ​​in a single variable. There are three array types available in PHP:

• Indexed array
• Associative array
• Multidimensional array

It’s very easy to create an array in PHP. You can create an array in PHP using the array() function or simply assigning [] in front of the variable.

Syntax of empty array

$exampleArray = []; 
$exampleArray = array();
$exampleArray = (array) null;

Basic example of empty array

<?php

// Create an empty array
$exampleArray = array();
// Push elements to the array
array_push($exampleArray, "developer", "diary");
// Display array elements
print_r($emptyArray);
?>

Using count() function you can use the number of element in array

$array=['Developer','Diary','ABC','Example'];
echo count($array); 
// outputs 4

array_combine() is used to create a new array using the key of one array as keys and the value of another array as values.

While array_merge() merges one or more arrays so that the value of an array is appended to the end of the first array.

Difference Between Array_merge() And Array_combine() In PHP

The PHP function array_key_exists() is used to check whether a key exists in an array or not.

Example

<?php
$a = array("fruit"=>"Mango","Car"=>"Maruti");
if (array_key_exists("fruit",$a)) {
  echo "Array Key exists!";
}else{
  echo "Array Key does not exist!";
}
?>

Using explode() php built in function we can create array from string.

Below is the basic example

<?php
$string = "PHP String to Array Example";
$php_array= explode(" ",$string);
print_r($php_array);
?>
// Output
Array ( [0] => PHP [1] => String [2] => to [3] => Array [4] => Example )

You can use the array_splice() or unset() function to remove an element from the PHP array.

unset() Example

<?php
$array1 = array(1, 5, 3, 4, 9, 11);
unset($array1[3]); // Unset the element
echo "Array elements after unset:<br>";
print_r($array1);
?>
// Output
Array elements after unset:
Array ( [0] => 1 [1] => 5 [2] => 3 [4] => 9 [5] => 11 )

array_splice() example

<?php
$arr = array(1, 5, 3, 4, 9, 11);
array_splice($arr,3,1);
print_r($arr);
?>
// Output
Array ( [0] => 1 [1] => 5 [2] => 3 [3] => 9 [4] => 11 )

Following types of sort function available in array

• sort(): sorting array in ascending order.
• rsort(): sorting array in descending order
• asort(): sort associative array in ascending order, by value
• ksort(): sort associative array in ascending order, by key
• arsort(): sort associative array in descending order, by value
• krsort(): sort associative array in descending order, by key

using json_encode() function we can convert a JSON string to an array in PHP.

According to the official PHP doc, there is no difference between the count() or sizeof() function in PHP, which means that both are the same, which means that the sizeof() function is just the alias of the function count is, i.e. size() uses the same as the count function below.

You can use array_unique() function to remove duplicate values ​​from PHP array. This means that if two or more array values ​​are the same, the first appearance is kept and the other is discarded.

array_unique() Example

<?php
$a=array("a"=>"red","b"=>"green","c"=>"red");
print_r(array_unique($a));
?>
// Output
Array ( [a] => red [b] => green )

Using array_rand() function we can get random value from PHP array.

Example : Following example every refresh you will get different value

<?php
$a=array("red","green","blue","yellow","brown");
$random_keys=array_rand($a,3);
echo $a[$random_keys[0]]
?>

Array PUSH and POP are PHP built-in functions and are used to work with an array.

Array push is used to add elements to the end of an array

Example

<?php
$a=array("A","B");
array_push($a,"C","D");
print_r($a);
?>
// Output
Array ( [0] => A [1] => B [2] => C [3] => D )

Array pop removes and returns the value of the last element of an array.

Example

<?php
 $stack = array("A", "B", "C", "D");
 echo $result = array_pop($stack); // prints D
?>