PHP function array_diff_key() used to compare the key names of two arrays and return the difference

Example

Compare the key names of two arrays and return the difference set:

<?php
$a1=array("a"=>"red","b"=>"green","c"=>"blue");
$a2=array("a"=>"red","c"=>"blue","d"=>"pink");

$result=array_diff_key($a1,$a2);
print_r($result);
?>

Definition and usage

array_diff_key() function Used to compare the key names of two (or more) arrays and return the difference.

This function compares the key names of two (or more) arrays and returns a difference array that includes everything in the compared array (array1) but not in any other parameter array (array2 or array3, etc.).

Syntax

array_diff_key(array1,array2,array3...);

Parameters	Description
array1	Required. The first array to compare with other arrays.
array2	Required. The array to compare to the first array.
array3,...	Optional. Additional array to compare with the first array.

Technical details

Return value:	Returns a difference array, which includes Returns all keys that are in the array being compared (array1), but not in any of the other argument arrays (array2 or array3, etc.).
PHP version:	5.1+

More examples

Example 1

Compare the key names of two numerical arrays and return the difference set:

<?php
$a1=array("red","green","blue","yellow");
$a2=array("red","green","blue");

$result=array_diff_key($a1,$a2);
print_r($result);
?>

Example 2

Compare the key names of three arrays and return the difference set:

<?php
$a1=array("a"=>"red","b"=>"green","c"=>"blue");
$a2=array("c"=>"yellow","d"=>"black","e"=>"brown");
$a3=array("f"=>"green","c"=>"purple","g"=>"red");

$result=array_intersect_key($a1,$a2,$a3);
print_r($result);
?>

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