array_funcs.php

// key = value
array_reduce($input, function ($carry, $item) {
	$carry[$item['x']] = $item['y'];
	return $carry;
}, []);

// key = value, from array with keys
array_reduce(array_keys($input), function($carry, $key) use ($input) {
	$carry[] = $input[$key]['x'];
	return $carry;
}, []);

// extract column (if array_column were to be missing)
array_map(function($item) {
	return $item['role'];
}, $input);