php - submit form running twice?

im using basic isset/form php filelike this:

if (isset($_POST['submitproduct']) ){ 
if (isset($_FILES['imageupload'])){  *some code* ..}

 

    productname
    
    

    

so i think this fairly normal routine, the form submits, it gets the data and adds it to sql database, no errors here, but after he is finished with the php script the browser for some reason doesnt skip isset($_POST['submitproduct'] like it was submited again for some reason, which obv throws error in the following code since no variables are set? I have coded similiar scripts like this base on if isset $_POST but this is the first time i got this error, only difference is, its my first time using encytpe. I tried to put header(location) to exit the script after it finish, but he just ignores it, im really clueless about this behavoiour , can anyone help?