PHP Paywall Form Outputs Black Screen - php

Question

I wrote a basic PHP script that contains a form that is supposed to when submitted open a Paypal buy now dialog and then echo "paid" once it has been paid.
For some reason it just shows a black screen with a small square after submitting the first form. It never gets to the paypal button form.
I have tried passing variables through paypal to keep them when it returns to the page and the php syntax checker detects zero issues.
Here is the code:
if(!isset($_POST["form1"])) {
if (!isset($_POST["payment_status"])) {
echo '<form action="article.php" method="post" ><input type="url" name="logo" placeholder="your .PNG logo" size="14"><input type="text" name="title" placeholder="title" size="14"><input type="hidden" name="form1" value="form1" size="14"><input type="submit" name="submit" value="submit"></form>';
}
}
if(isset($_POST["form1"])) {
header('Content-type: image/png');
$title = $_POST["title"];
$image3 = $_POST["logo"];
$dataa = $title;
$dataa .= $logo;
echo '<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<br>
<input name="currency_code" type="hidden" value="USD">
<input name="shipping" type="hidden" value="0.00">
<input name="tax" type="hidden" value="0.00">
<input type="hidden" name="amount" value="0.20">
<input name="return" type="hidden" value="http://example.com/article.php/?data=$dataa">
<input name="cancel_return" type="hidden" value="http://example.com">
<input name="notify_url" type="hidden" value="http://example.com/article.php">
<input name="cmd" type="hidden" value="_xclick">
<input name="business" type="hidden" value="example#example.com">
<input name="item_name" type="hidden" value="digital download">
<input name="no_note" type="hidden" value="1">
<input type="hidden" name="no_shipping" value="1">
<input name="lc" type="hidden" value="EN">
<input name="bn" type="hidden" value="PP-BuyNowBF">
<input name="custom" type="hidden" value="pass form data here">
<input type="submit" name="submit" value="download survey results $2">
<img alt="" border="0" src="https://www.paypalobjects.com/fr_FR/i/scr/pixel.gif" width="1" height="1">
</form>';
}
if (isset($_POST["payment_status"])) {
$payment_status = $_POST['payment_status'];
if ($payment_status == "Completed") {
echo "paid";
echo "<h1>Here is the unlocked article</h1>";
}
}
else {
echo "";
}
?>