PHP页面保护(PHP page protection)

 我在我的网站上销售数字产品，并且我想设置某种页面保护。 我的客户通过PayPal付款。 我有一个“提交”页面上的链接到PayPal结帐，并已设置我的结帐重定向到“信息”页面。 信息页面是我想要保护的内容。 
 
 这里是我到目前为止的代码，但由于某种原因，它不工作，我不断收到“else”语句... 
 
<div id="info">
<ul>
<li>
<?php 
if ( $_SERVER['HTTP_REFERER'] == "https://www.paypal.com/" ){

echo 'information...';

}else{
echo 'You need to pay first...';
}
?>
</li>
</ul>
</div>
 
 有人看到我做错了什么？ 或者有更好的选择？ 
 
 谢谢！ 

I am selling digital products on my site, and I want to set up some kind of page protection. My customers are paying through PayPal. I have a link on the "submit" page to PayPal checkout, and have set up my checkout to redirect to the "information" page. The information page is what I want to protect.
 
Here's the code I have so far, but for some reason it's not working, I keep getting the "else" statement...
 
<div id="info">
<ul>
<li>
<?php 
if ( $_SERVER['HTTP_REFERER'] == "https://www.paypal.com/" ){

echo 'information...';

}else{
echo 'You need to pay first...';
}
?>
</li>
</ul>
</div>
 
Anybody see what I'm doing wrong? Or have a better option?
 
Thanks!

原文：https://stackoverflow.com/questions/7266025