array_diff_key(): Difference between two arrays with respect to Keys

$new_array = array_diff_key ($array1, $array2,....);

Comparison of two or more arrays are done by using values in array_diff()

Example with two arrays

$first=array('One' =>'First','Two'=>'Second','Three'=>'Third','Four'=>'Fourth');
$second=array('One'=> 'First','Two'=>'2nd','Third'=>'3rd','Fourth'=>'Fourth');

$result1=array_diff_key($first,$second);
while (list ($key, $val) = each ($result1)) {
echo "$key -> $val <br>";
}

Three -> Third 
Four -> Fourth 

Example 1: Comparing Three Arrays

<?php
$first = array('a' => 'apple', 'b' => 'banana', 'c' => 'cherry');
$second = array('a' => 'apple', 'd' => 'date');
$third = array('b' => 'banana', 'e' => 'elderberry');
$result = array_diff_key($first, $second, $third);
print_r($result);  // Output: ['c' => 'cherry']
?>

Example 2: Using Numeric Keys

<?php
$array1 = array(1 => 'one', 2 => 'two', 3 => 'three');
$array2 = array(2 => 'two', 4 => 'four');
$result = array_diff_key($array1, $array2);
print_r($result);  // Output: [1 => 'one', 3 => 'three']
?>

Example 3: Mixed Key Types in Arrays

<?php
$array1 = array('a' => 'apple', 2 => 'banana', 'c' => 'cherry');
$array2 = array(2 => 'banana', 'b' => 'blueberry');
$result = array_diff_key($array1, $array2);
print_r($result);  // Output: ['a' => 'apple', 'c' => 'cherry']
?>

Example 4: Comparing with an Empty Array

<?php
$array1 = array('a' => 'apple', 'b' => 'banana');
$array2 = array();
$result = array_diff_key($array1, $array2);
print_r($result);  // Output: ['a' => 'apple', 'b' => 'banana']
?>

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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