PHP | array_key_exists() Function

Pre-requisite: PHP | array_keys() Function

The array_key_exists() is an inbuilt function of PHP and is used to check whether a specific key or index is present inside an array or not. The function returns True if the specified key is found in the array otherwise returns false.

Syntax:

boolean array_key_exists($index, $array)

Parameters: This function takes two arguments and are described below:

$index (mandatory): This parameter refers to the key that is needed to be searched for in an input array.
$array (mandatory): This parameter refers to the original array in which we want to search the given key $index.

Return Value: This function returns a boolean value i.e., TRUE and FALSE depending on whether the key is present in the array or not respectively.

Note: Nested keys will return result as FALSE.

Examples:

Input: $array = array("ram"=>25, "krishna"=>10, 
                            "aakash"=>20, "gaurav")
       $index = "aakash"
Output : TRUE

Input : $array = ("ram", "krishna", "aakash", "gaurav");
        $index = 1
Output : TRUE

Input : $array = ("ram", "krishna", "aakash", "gaurav");
        $index = 4
Output : FALSE

Below programs ilustrates the array_key_exists() function in PHP:

In the following program we will see how we can find a key inside an array that holds key_value pair.

<?php 
// PHP function to illustrate the use 
// of array_key_exists() 
function Exists($index, $array) 
{ 
    if (array_key_exists($index, $array)){ 
        echo "Found the Key"; 
    } 
    else{ 
        echo "Key not Found"; 
    } 
} 
  
$array = array("ram"=>25, "krishna"=>10,  
                "aakash"=>20, "gaurav"); 
$index = "aakash"; 
print_r(Exists($index, $array)); 
?> 

Output:

Found the Key

If no key_value pair exits, as in the below case, then the array takes the default keys i.e. numeric keys starting form zero, into consideration and returns True as far as the $index limit ranges.

<?php 
// PHP function to illustrate the use of 
// array_key_exists() 
function Exists($index, $array) 
{ 
    if (array_key_exists($index, $array)) { 
        echo "Found the Key"; 
    } 
    else{ 
        echo "Key not Found"; 
    } 
} 
  
$array=array("ram", "krishna", "aakash", "gaurav"); 
$index = 2; 
print_r(Exists($index, $array)); 
?> 

Output:

Found the Key

Reference:
http://php.net/manual/en/function.array-key-exists.php

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