The difference between isset() and array_key_exists() functions in PHP

isset() function is a built-in function in PHP that checks whether a variable has been set and is not NULL. This function also checks if the declared variable, array or array key has a null value, if so, isset() returns false, it returns true in all other possible cases.

Syntax:

bool isset( $var, mixed )

Parameters: This function accepts multiple parameters. The first parameter of this function is $var. This parameter is used to store the value of the variable.

Program:

<?php  
  
// 声明一个数组
$array = array(); 
  
// 使用isset功函数
echo isset($array[&#39;geeks&#39;]) ? &#39;array is set.&#39; :  
    &#39;数组未设置&#39;; 
?>

Output:

数组未设置

array_key_exists() function

array_key_exists() function is also predefined in PHP Function that checks whether an index or a specific key exists in an array. It does not evaluate the key's value for any null value. It returns false if it does not find the key in the array, and true in all other possible cases.

Syntax:

bool array_key_exists( $key, $array )

Parameters: This function accepts the above two parameters as described below:

$key: This parameter is used to store the value to be checked.

$array: This parameter is used to store the array with the keys to be checked.

Program:

<?php  
  
// 创建一个数组
$array = array( 
     &#39;name&#39; => null, 
); 
  
// 使用array_key_exists函数
echo array_key_exists(&#39;name&#39;, $array)  
? &#39;array key exists&#39; : &#39;array key does not exist&#39;; 
?>

Output:

array key exists

The main difference between the isset() and array_key_exists() functionsis that the array_key_exists() function will definitely Tells if the key exists in the array, whereas isset() only returns true if the key/variable exists and is not empty. When array_key_exists does not exist, isset() also does not render an error when the array/variable exists.

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