mysql updating multiple column values from array variable

"UPDATE product_list 
set 
product_name='$product_name', 
product_category ='$product_category', 
product_price='$product_price',
product_description='$product_description',
product_size_category='$size_category'
where product_id='$product_id'
"

$sql = "UPDATE product_list SET product_name='".$product_name."',product_category='".$product_category."',product_price='".$product_price."',product_description='".$product_description."',size_category='".$size_category."'";