array_diff_key

Definition and usage

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

The function compares the key names of two (or more) arrays and returns an array of differences that include all key names in the array being compared ( array1 ) but not in any other parameter array ( array2 or array3 , etc.).

Example

Example 1

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

 <?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 ) ;
?>

Try it yourself

Example 2

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

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

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

Try it yourself

Example 3

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

 <?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_diff_key ( $a1 , $a2 , $a3 ) ;
print_r ( $result ) ;
?>

Try it yourself

grammar

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

illustrate

array_diff_key() function returns an array that includes all keys in the array being compared but not in any other parameter array.