array array_diff_key ( array array1, arrayarray2 [, array $...] );

<?php
   input1 = array(1, 2, 3, 4, 5);input2 = array(4, 5, 6);

   result = array_diff_key(input1, input2);
   print_r(result);
?>

Array
(
    [3] => 4
    [4] => 5
)

<?php
   input4 = array(1, 2, 3);input5 = array(4, 5, 6);

   result = array_diff_key(input4, input5);
   print_r(result);
?>

Array
(
)

<?php
   input1 = array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow", "f"=>"yellow");input2 = array("a"=>"red","b"=>"green","c"=>"blue");

   result = array_diff_key(input1, input2);
   print_r(result);
?>

Array
(
    [d] => yellow
    [f] => yellow
)