Question

I have two arrays, one is a subset. I need to re-order the larger array so that all the items from array one are at the top of it.

array('c', 'e');
array('a', 'b', 'c', 'd', 'e', 'f', 'g');

I want the 2nd array to look like this:

array('c', 'e', 'a', 'b', 'd', 'f', 'g');

“c” and “e” are at the top of it.

Answer 1

You can use usort and move the elements up if the other array contains the element:

e.g:

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

usort($b, function($x, $y) use($a) {
    return in_array($x, $a) ? -1 : 1;
});

This won’t take into consideration the order of $a, but will allow duplicate elements (if required).