Detect clients with Proxy Servers via PHP [duplicate]

Answer 1

Even if it's an old question, I've had to check for proxy and unfortunatly none of the answers give good result.

After searching, I've found a better method. In order to understand this way of doing, just create a small page with this code:

  $val)
 {
     echo $key."
\n";  
 }
 ?>

Run it direclty from your server. You'll see all keys from the header your server is sending. Then run the same script through a Proxy. You'll see (depending on the Proxy) 3 possible results:

1. the Proxy add news keys/values
2. the Proxy don't send all the original keys/values so some are missing.
3. the Proxy send exactly the same keys/values but not in same order
4. the Proxy send exactly the same keys/values, in same order

The 4th case can happen but others are the most frequent. So you just have to create an array with the key/value from your server (based on the result when you run the script without a Proxy) and compare the keys/values from $_SERVER. If you don't have exacty the same keys/values (less, more or in other order) you can assume the page came from a Proxy.

Notice I agree with those saying in some cases Proxy can be use in a "legal".