The PHP array_key_exists() function checks if a specific key exists in the array. The function returns TRUE if the key is present, else it returns FALSE. array_key_exists() function works for both indexed arrays and associative arrays. For indexed arrays, index is the key.

Syntax – array_key_exists()

array_key_exists( key, array)

Parameters

• $key (mandatory): This parameter refers to the key/index 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 $key.

Function Return Value

array_key_exists() returns boolean value TRUE if the key exists and FALSE if the key does not exist.

Example:-

In this example, we will take an associative array with key-value pairs, and check if a specific key "m" is present in the array.

<?php
    $array1 = array("a"=>"apple", "b"=>"banana", "m"=>"mango", "o"=>"orange");
    $key = "m";
    if (array_key_exists($key, $array1)) {
       echo "Key exists in the array!";
    } else {
       echo "Key does not exist in the array!";
    }
?>

Output:-

array_key_exists() returns TRUE for the given array and specified key. So, if the block is executed.

Example 2: array_key_exists() for Indexed Array

In this example, we will check if a specific index (key) is present in the array.

<?php
    $array1 = array("Ram", "Sita", "Lakshman", "Bharat");
    $key = "3";
    if (array_key_exists($key, $array1)) {
      echo "Key exists in the array True!";
    } else {
      echo "Key does not exist in the array False!";
    }
?>

Output

The array is also printed to the console to understand the index of items in the array.