report error 404 by email with last accessed URL - php

Question

I'm making a page 404 with button for user report that site have a problem. The idea is when user click on button, I receive a email with information of the last page accessed...
The problem is that I'm using the php variable '$_SERVER['HTTP_REFERER']' and this ever return a null value. I found this question (In what cases will HTTP_REFERER be empty) and I came to the conclusion that this variable is not the solution.
This is my .htacess
RewriteEngine on
ErrorDocument 404 http://example.com/erro.php
#ErrorDocument 404 /erro.php #this doesnt work... redirect doesnt work
On page erro.php I have code with function email that are working without problem, but I need some manner to take last accessed page that generate error.
On page erro.php I'm trying use:
echo $_SERVER['HTTP_REFERER']; // return null value
echo $_SERVER['REQUEST_URI']; // return page http://example.com/erro.php
I try use alternative with jQuery (https://stackoverflow.com/a/2415645/2761794):
On page erro.php
$(document).ready(function() {
var referrer = document.referrer;
alert(referrer); // return null value
});
Some suggestion to take last accessed URL on page erro.php for send by email?

Answer 1

As you are willing to work with mod_rewrite anyway and have PHP there is a slightly different approach.
First you could detect for a request that is for a file or directory that is not there and pass that to the PHP script with a rewrite.
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
Rewriterule ^(.*) /erro.php?error_path=$1 [R=301,L]
Depending on your exact setup you may need to tweak that last line perhaps to
Rewriterule ^(.*) http://example.com/erro.php?error_path=$1 [R=301,L]
I find that mod_rewrite is somewhat akin to voodoo and can sometimes need a little "try it out and see what works".
Then in your erro.php file:
<?php
$badfile = $_GET['error_path']; // the URL that 404'd
http_response_code(404); // send the 404 header code
// ... your other code
The end result for the visitor should be almost the same but you would have access to the data you need.
Much of the rewrite directive came from this question: htaccess errordocument 404 and pass url to path
For more on setting response codes in php: http://php.net/manual/en/function.http-response-code.php
mod_rewrite cheat sheet: http://www.cheatography.com/davechild/cheat-sheets/mod-rewrite/
The official doc on mod_rewrite: http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html