how to merge between two arrays by index : i have two arrays .. first array like this : 

    $questions = [
                "type" => "form",
                "controls" => []
            ];

and second array is filled by foreach loop like this :

    $count = 0;
    foreach($x as $y){
    	$controls [
    	"id" => $y.$count,
    	"id2" => $y.$count+1,
    	]
    
    	$count++;
    }

i want to merge all values from the second array to `controls` index from first array 

any help please 