Return to a calling page when submitting a form

<form action="myfile.php" name ="formSubmit" method="POST" enctype="multipart/form-data">
                <label>Product Code</label>
                <input type="text" name="productCode"><br>
                <label>Product Image</label>
                <input type="file" name="myfile1" />
                <input type="submit" value="Add Product">
                </form>

<?php
// connect to database
$dbname = mysql_connect("************", "user","password")or die('Cannot select database');
mysql_select_db("mydb")or die('Cannot select database');

// if unable to connect display error
if (!$dbname ) {
echo "Unable to establish connection to database server";
exit;
}

if (!mysql_select_db('mydb', $dbname )) {
echo "Unable to connect to database";
exit;
}

if (($_FILES["myfile1"]["type"] == "image/gif")
|| ($_FILES["myfile1"]["type"] == "image/jpeg") // only allow: .gif & .jpeg
&& ($_FILES["myfile1"]["size"] < 2000000)) // limitation of size: 2MB
{
if ($_FILES["myfile1"]["error"] > 0) // error occurs during uploading
{
echo "Return Code: " . $_FILES["myfile1"]["error"] . "<br />";
} //end if
else
{
// show the basic information of uploaded files
echo "Upload: " . $_FILES["myfile1"]["name"] . "<br />";
echo "Type: " . $_FILES["myfile1"]["type"] . "<br />";
echo "Size: " . ($_FILES["myfile1"]["size"] / 1024) . " Kb<br />";
echo "Temp file: " . $_FILES["myfile1"]["tmp_name"] . "<br />";

// check whether the file exists in the target folder
if (file_exists("upload/" . $_FILES["myfile1"]["name"])){
echo $_FILES["myfile1"]["name"] . " already exists. ";
} //end if

// do the uploading: moving the file from temporary folder to the target folder
else
{
move_uploaded_file($_FILES["myfile1"]["tmp_name"],
"upload/" . $_FILES["myfile1"]["name"]);
echo "Stored in: " . "upload/" . $_FILES["myfile1"]["name"] . "<br />";

//store filename in the database together with the product code
$name = $_FILES["myfile1"]["name"];
$result = mysql_query("insert into images values ('$productCode','$name')");
echo "Product " . $productCode . " successfully added to the database." . "<br />" ;
} //end else
} //end else
} // end if

else
{
echo "Invalid file";
}
echo "finish";
header("Location: admin.php");
//header("Location: ".htmlentities($_SERVER['HTTP_REFERER']));
//header("Location: ".$_POST["formSubmit"]);

?>