array_key_exists() : Check if given key or index is available inside input array

This function Searches for presence of a input key.

bool = array_key_exists ($key_to_search, $input_array);

$key_to_search : Required , key to search inside the $input_array.
$input_array : Required , array inside which the key will be searched.

Output is TRUE if key is found inside array , otherwise FALSE

Example 1

$input=array(1,2,3,4);

if(array_key_exists(2,$input)){
echo "Key is available ";	
}else{
echo "Key is NOT available ";	
}

Output is here.

Key is available

Example 2

$input=array('One' ,'Two','Three');

if(array_key_exists(0,$input)){
echo "Key is available ";	
}else{
echo "Key is NOT available ";	
}

Output is here

Key is available

Example 3

$input=array('One' =>1,'Two'=>2,'Three'=>3,'Four'=>'Fourth');

if(array_key_exists('Three',$input)){
echo "Key is available ";	
}else{
echo "Key is NOT available ";	
}

Output is here.

Key is available

array_key_exists and Null value

For Null value array_key_exist() returns True, however isset() returns False

$input=array('One' =>1,'Two'=>null);

if(array_key_exists('Two',$input)){ // True 
echo "Key is available ";	// this is the output
}else{
echo "Key is NOT available ";	
}
echo "<br>";
//// 
echo var_dump(isset($input['Two'])); // bool(false)

Example: Validating Form Data

$form_data = ['name' => 'John', 'email' => 'john@example.com'];
if (array_key_exists('name', $form_data)) {
    echo "Name field exists.";
} else {
    echo "Name field is missing.";}

Output

Name field exists.

Example: Handling Multidimensional Arrays

$data = [
    'user' => ['name' => 'Alice', 'age' => 25],
    'order' => ['id' => 123, 'total' => 50]
];
if (array_key_exists('name', $data['user'])) {
    echo "Name exists in user array.";
}

Output

Name exists in user array.

Example: Comparing array_key_exists() and isset()

$arr = ['name' => null];
echo isset($arr['name']);  // Output: false
echo '<br>';
echo array_key_exists('name', $arr);  // Output: true

Explanation:
Form Validation: Shows practical usage of `array_key_exists()` for validating whether specific keys exist in user-submitted data.
Handling Multidimensional Arrays: Demonstrates working with nested arrays, common in complex applications.
Comparison with `isset(): Highlights the differences between `isset()` and `array_key_exists()` when dealing with `null` values.

Function	Details
in_array()	Search for value inside Array. Returns TRUE or FALSE
array_search()	Search for value inside Array. Returns the key if found, FALSE otherwise
array_keys()	Array of keys for matching values, FALSE otherwise

Array REFERENCE

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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