Get array keys object PHP

Ok. I need to get keys, i think they they are called keys.

When i var_dump object i get

object(stdClass)#6 (7) { ["id"]=> string(1) "2" 
["title"]=> string(14) "Old wood table" 
["price"]=> string(2) "25" 
["size_w"]=> string(2) "65" 
["size_h"]=> string(2) "50" 
["size_l"]=> string(2) "60"
["material"]=> string(4) "wood" }

Code itself

$catalog = new Catalog('furniture',2);
if(!$catalog->exists()){
    die('Product dose not exist');
}else{
    $product = $catalog->data();
}
echo $product->title;
var_dump($product);
$productsArray = get_object_vars($product);

foreach($productsArray as $attribute){
   echo  $attribute . '<br/>';  
}

For now i am getting back

2
Old wood table
25
65
50
60
wood

Result i need

id-2
title-foo
price-25
size_w-65
size_h-50
size_l-60
material-wood

I tried to use key(array) and next(array)

foreach($productsArray as $attribute){

   echo key($productsArray) . '- ' . $attribute . '<br/>';
   next($productsArray);
}

but the results was

title- 2
price- Old wood table
size_w- 25
size_h- 65
size_l- 50
material- 60
- wood

It seems like it's skipping id key. Any ideas? Thanks