oh ... I thought you meant that you use the $price variable in all of your scripts.
That you update it with one script and read it / display it with another.
What happens when you change this:
$price=(float)$row;// converts to float
$price=$price + $price;
$price=$price + $row;
$price=number_format($price, 2, '.', '');
I don't know what the float part is all about, nor the GLOBAL part.
What is that supposed to do for you?