Question : PHP File Access Control Handler

I would like to create a HTTP handler using preferably a PHP (or possibly Python) script which simply validates some session variables prior to permitting a download (be it an image to be shown on a web page, or a ZIP file):

i.e.
URI: http://mydomain.com/res.php?id=123
File Path: /home/vhosts/mydomain.com/private/res/download.zip (No HTTP Access)

I understand that introducing a PHP handler will incur some small overhead. But is there a PHP solution to the following which incurs exactly the same additional overhead regardless of file size.

I hope that I have explained this clearly.

What is the most efficient way to accomplish this with PHP? Is there a way to send a file as the response (in a similar way to the default HTTP download handler that is used to convey images, ZIPs, etc)?

Script pseudo-code:

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if ($authorized) {
   send ('/home/vhosts/mydomain.com/private/res/download.zip');
}
else {
   echo 'Access denied.';
   exit;
}

Answer : PHP File Access Control Handler

No real difference in overhead - the file must still be read and sent via HTTP no matter how you do it. You must have enough memory to load the entire file.

To show an image on a web page you would just do something like this:
header('Content-type: image/jpg');

Then pass the binary image file to the browser output stream. But it might be easier to just give the client a regular link.

Best regards, ~Ray