Array Questions in PHP interviews

PHP Array is a special type of variable that stores multiple values in a single variable. There are 3 types of array available in PHP they are

• Indexed arrays
• Associative arrays
• Multidimensional arrays

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

$array1=array() or $array1=[];

You can use count() function to count the number of elements in a PHP Array.

$array=['ram','ravi','ajay','vijay'];
echo count($array); // outputs 4

array_combine() is used to creates a new array by using the key of one array as keys and using the value of another array as values. Whereas array_merge() merges one or more than one array such that the value of one array appended at the end of the first array.

PHP array_key_exists() Function is used to check a key exist or not in an array.

Example Uses

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

PHP explode() function is used to create an array from a string in PHP. Explode function breaks a string using a delimiter into an array.

Below is the basic syntax to convert a string to an array in PHP

<?php
$string = "This is a string in PHP";
$php_array= explode(" ",$string);
print_r(" ",$php_array);
?>

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

There are basically three types of arrays available in PHP. They are:

• Indexed arrays
• Associative arrays
• Multidimensional arrays

PHP functions for Sorting Arrays are

• sort(): Used for sorting arrays in ascending order.
• rsort(): used for sorting arrays in descending order
• asort(): used to sort associative arrays in ascending order, by value
• ksort(): used to sort associative arrays in ascending order, by key
• arsort(): used to sort associative arrays in descending order, by value
• krsort(): used sort associative arrays in descending order, by key

json_encode() function is used to convert a JSON string to an array in PHP.

Syntax

json_decode(string, assoc, depth, options)

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

You can use the array_unique() function to remove duplicate values from PHP Array. That means if there are two or more array values are the same, the first appearance will be kept and the other will be removed.

array_rand() function is used to get random value from PHP array.

Usage

<?php
$a=array("apple","banana","grapes","mango","orange");
echo $random_value=array_rand($a);
?>

The difference between array PUSH and POP are as follows - 

Array PUSH and POP both are inbuilt PHP functions and used to work with an array.

Array push is used to add one or more elements onto the end of an array

Example

<?php
$a=array("car","truck");
array_push($a,"van","plane");
print_r($a);
?>

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

Syntax

<?php
$stack = array("orange", "banana", "apple", "raspberry");
echo $fruit = array_pop($stack); // prints raspberry

?>