Resize image in a square while maintaining proportion of the original PHP image

What happens is this: I'm pulling some product photos from an XML link, and the images come in different sizes.

I currently use a code that takes the image and resizes it to 200x200, but images with different height and width obviously make it strange.

$img_path     = (string) $googleBase->image_link;

$destination  = $img_server_folder_path;

$stlName = "stl";

$dimensions = getimagesize($img_path);

$w = $dimensions[0];
$h = $dimensions[1];

$ratios = [
    'small' => 200/$w
];

$resource = imagecreatefromstring( file_get_contents( $img_path ) );

foreach ( $ratios as $name => $ratio ) {

$w2 = $w * $ratio;
$h2 = round($h * $ratio);

$output = imagecreatetruecolor($w2, $h2);

if ( ! file_exists( $img_server_folder_path . $row['NomeLoja'] ) ) {
    mkdir( $img_server_folder_path .    $row['NomeLoja'], 0777, true );
}

// definimoso caminho no servidor para salvar a imagem | evita erro de acesso a pasta
$imagem = $img_server_folder_path . $row['NomeLoja'] . "/" . $googleBase->id . "_" . $stlName . ".jpg";

imagecopyresampled($output, $resource, 0, 0, 0, 0, $w2, $h2, $w, $h);

imagejpeg($output, $imagem, 100);

imagedestroy($output);

What I need to do is create a white square, with 200x200, and then put the image of the product in that square, respecting its proportion but making it whole fit on the white square, is it possible?