<?php

function merge_books($book1, $book2)
{
  
  
}


// array_keys(somearray) returns an array containing keys of somearray
// in_array(something, somearray) returns true if something exists in somearray


$friend_book1 = Array('Humpty' => '111-111-1111', 'Dumpty' => '222-222-2222', 
                      'Duh' => '333-333-3333', 'Oops' => '444-444-4444', 'Huh' => '555-555-5555');
$friend_book2 = Array('Dumpty' => 'dumpty@uva.edu', 'Duh' => 'duh@uva.edu', 
                      'Humpty' => 'humpty@uva.edu', 'Huh' => 'huh@uva.edu', 
                      'Wacky' => 'wacky@uva.edu');

$result = merge_books($friend_book1, $friend_book2);
print($result); 

?>