PHP array_diff_key () Function

PHP array_diff_key () Function

The array_diff_key () Function in PHP compares the keys from array1 against the keys from arrays. It returns an array containing all the entries from array1 whose keys are absent from all other arrays.

This function is like array_diff () except that in this the comparison is made based on keys instead of the values.

Syntax

array_diff_key ( array $array1 , array $array2 [, array $... ] )

Parameter

array1(required)- This parameter signifies the input array to compare from.

array2(required)- This parameter signifies the input array to compare against.

array3….(optional)- It represents more arrays to compare against

Return

This function returns an array containing all the entries from array1 whose keys are absent from all other arrays.

Example 1

 "Reema", 2 => "Akash", 3 => "Sukla", 3 =>"Varun",4=>"Mukta",5=>"Amar");
 //initializing array2
 $array2 = array(1 => "Reema", 2 => "Akash", 3 => "Tisha", 3 =>"Varun");
 //computing the difference of array1 and array2 keys
 $differnce = array_diff_key($array1,$array2);
 //printing the difference 
 print_r($differnce);
 ?> 

Output

Array
 (
     [4] => Mukta
     [5] => Amar
 ) 

Example 2

 "Reema", 2 => "Akash", 3 => "Sukla", 4 =>"Varun",5=>"Mukta",6=>"Amar");
 //initializing array2
 $array2 = array(1 => "Reema", 2 => "Akash", 3 => "Tisha", 4 =>"Varun");
 //initializing array3
 $array3 = array(1 => "Rahul", 2 => "Akash", 3 => "Tisha", 4 =>"Varun",5=>"Reema"); 
 //computing the difference of the keys
 $differnce = array_diff_key($array1,$array2,$array3);
 //printing the difference
 print_r($differnce);
 ?> 

Output

Array
 (
     [6] => Amar
 ) 

Example 3

1,2=>2,3=>3,4=>4,5=>5,6=>6,7=>7,8=>8,9=>9,10=>10);
 //initializing array2 with odd number
 $array2 = array(1=>1,3=>3,5=>5,7=>7,9=>9);
 //computing the difference of the keys
 $differnce = array_diff_key($array1,$array2); 
 //printing the difference i.e., even numbers
 print_r($differnce);
 ?> 

Output

Array(
     [2] => 2
     [4] => 4
     [6] => 6
     [8] => 8
     [10] => 10
 )