array_flip

The array_flip() PHP function changes all the keys in an array into values, and all the values into keys.

PHP

$a = array('apple' => 1, 'ibm' => 2, 'sun' => 3);
$flipped = array_flip($a);
print_r($flipped);
/*
Array (
	[1] => apple
	[2] => ibm
	[3] => sun
)
*/

To replicate this functionality in Ruby, we will use a Hash object, since arrays in Ruby don’t use associative key / value pairs.

Ruby

hash = { "apple" => 1, "ibm" => 2, "sun" => 3 };
flipped = hash.invert;
p flipped;
# => {1 => "apple", 2 => "ibm", 3 => "sun"}

In PHP, the array_flip() function will over write any conflicting keys. The Ruby invert() method behaves the same - any keys which are the same as other keys will overwrite the previous one.