how to upload image with fix width and height

$product_image1 = $_FILES['product_image1']['name'];

$source = $_FILES['new_image']['tmp_name'];

          $target = "../../media/product/".$product_image1;

        //  move_uploaded_file($source, $target);

          $imagepath = $product_image1;

          $save = "../../media/product/" . $imagepath; //This is the new file you saving

          $file = "../../media/product/" . $imagepath; //This is the original file

         

          list($width, $height) = getimagesize($_FILES['product_image1']['tmp_name']) ; 

          $modwidth = 150; 

          $diff = $width / $modwidth;

          $modheight = 155; 

          $tn = imagecreatetruecolor($modwidth, $modheight) ; 

          $image = imagecreatefromjpeg($_FILES['product_image1']['tmp_name']) ; 

          imagecopyresampled($tn, $image, 0, 0, 0, 0, $modwidth, $modheight, $width, $height) ; 

          

         imagejpeg($tn, $save, 75) ;