Array copy values to keys in PHP [duplicate]

I have this array:

$a = array('b', 'c', 'd');

Is there a simple method to convert the array to the following?

$a = array('b' => 'b', 'c' => 'c', 'd' => 'd');

Solution 1:

$final_array = array_combine($a, $a);

Reference: http://php.net/array-combine

P.S. Be careful with source array containing duplicated keys like the following:

$a = ['one','two','one'];

Note the duplicated one element.