To switch the position of keys and corresponding values in each element of an array, use the PHP function array_flip():
$a = array('1' => 'a', '2' => 'b', '3' => 'c');
$b = array_flip($a);
print_r($b);
And the output would be:
Array
(
[a] => 1
[b] => 2
[c] => 3
)