Grab URI from address line?

            <?
                if(!$HTTP_REFERER) {
                    $source = USER;
                }
                elseif(substr_count($HTTP_REFERER,$SERVER_NAME) > 0) {
                    $source = INTERNAL;
                }
                else {
                    $source = EXTERNAL;
                }
             ?>
 

        <H2>
            <?
                if($source == "USER") {
                    echo "404 - incorrect URL entered";
                }
                elseif($source == "INTERNAL") {
                    echo "404 - Internal link broken";
                }
                elseif($source == "EXTERNAL") {
                    echo "404 - Invalid link from $HTTP_REFERER";
                }
            ?>
            
        </H2>
        <? 
            if($source == "USER") {
                echo "You seem to have typed the url incorrectly.<br>We will take you to our home page at <a href=\"http://$SERVER_NAME\">$SERVER_NAME</a>.";
            }
            elseif($source == "INTERNAL") {
                echo "Whoops!  We seem to have a broken internal link.<br>";
                echo "Please tell the webmikester (<a href=\"mailto:webmike@mikesofchicago.org\">webmike@mikesofchicago.org</a>).<br>";
                echo "We will return you to <a href=\"$HTTP_REFERER\">$HTTP_REFERER</a>.";
            }
            elseif($source == "EXTERNAL") {
                echo "The page $HTTP_REFERER sent you to a page which doesn't exist on this site (${SERVER_NAME}).<BR>";
                echo "You may want to tell the site's webmaster to correct the link.<BR>";
                echo "We will take you to our home page at <a href=\"http://$SERVER_NAME\">$SERVER_NAME</a>.";
            }

        ?>