PHP HTTP Referrer

Question

I have a page which accepts POSTs from a remote site. I would like to detect the domain that these POSTs are coming from. I realize that it can be spoofed but it is better than nothing. I have tried accessing the HTTP_REFERER variable but it just returns null.

The page accepts POSTs from sources like PayPal (instant payment notifications) and other payment gateways.

How can I get the referring call?

Solution 1

You spelled Referer correctly. It should be:

$_SERVER['HTTP_REFERER']

Solution 2

$_SERVER['HTTP_REFERER'] 

with a single R, try var_dump($_SERVER) for more info.

Solution 3

This works for me pretty well:

https://stackoverflow.com/a/17958676/2635701

<form action="http://www.yourdomain.com/subscribe" 
   method="POST" 
   onsubmit=
      "document.getElementById('www.yourdomain.com.referrer').value=window.location;" >
    <!-- hidden input for field starts with a domain registered by you 
    just so that it's unlikely to clash with anything else on the page -->
    <input type="hidden" id="www.yourdomain.com.referrer" name="referrer"/>
    your email: <input name="email" type="text"/>
    ... rest of form ...
    <input type="submit" value="Subscribe"/>
</form>

Solution 4

You are right that the referrer is easy to spoof, however there is a better solution. Read the ipn documentation in which they mention validation mechanisms. Never trust the user.

View more solutions

Comments

[aaronfarr]

Thanks, that was a typo in the question. Still not returning anything in the code. Strange!

[AbiusX]

Referrer is the english word, but in PHP its Referer.

[AbiusX]

It might simply be null. Not all browsers send referers

[aaronfarr]

Thanks. Have implemented the IPNs properly. But I would like to use the same page to filter other IPNs other than paypal. So using the referer seemed like a logical way of doing it. Any suggestions how this could be done?

[Dũng Trần Trung]

What if javascript is disabled?

[Jordan]

Fun Fact: The misspelling of referrer originated in the original proposal by computer scientist Phillip Hallam-Baker to incorporate the field into the HTTP specification.[4] The misspelling was set in stone by the time of its incorporation into the Request for Comments standards document RFC 1945; document co-author Roy Fielding has remarked that neither "referrer" nor the misspelling "referer" were recognized by the standard Unix spell checker of the period. Source: [en.wikipedia.org/wiki/HTTP_referer]