Facebook crawler redirect to force displaying own opengraph meta-tags

Question

For my website, I use the opengraph to send the right data to the crawler.

On the top of all pages on my website, I include the opengraph-script, like this:

if (preg_match("/facebookexternalhit/is", $_SERVER['HTTP_USER_AGENT'])) {
    include("./facebook-crawler.php");
    exit();
}

facebook-crawler.php:

        ## Infos for Crawling
        $server_path                = $_SERVER['REQUEST_URI']; 
        $expl_path                  = explode("/", $server_path);
        $page_title                 = $expl_path[1];
        $page_data                  = "";
        $page_path_display          = "";

        if (isset($expl_path[2]) && $expl_path[2]!="") {
            $page_data              = $expl_path[2];
            $page_path_display      = "/".$page_title."/".$page_data;   
        } elseif ($page_title!="") {
            $page_path_display      = "/".$page_title."/"; 
        } else {
            $page_path_display      = "/";  
        }

function show_fbmeta_home() {

        global $site_url, $site_url_displayname, $fb_app_id, $fb_admins, $page_path_display, $count_cars, $count_member, $count_ps;

        get_statistics_general(); 

        $use_title      = "Lunatics Car Club Austria - est. 2014 - {Beta}";
        $use_text       = $count_member." Mitglieder, ".$count_cars." Autos, ".$count_ps."PS. Besuch unsere Website um mehr zu Erfahren!";
        $use_type       = "article";
        $use_pic        = $site_url."/images/home/r32-gruppenbild.jpg";

        $meta_string = 
        '<meta property="og:title" content="'.$use_title.'" />
        <meta property="fb:app_id" content="'.$fb_app_id.'"/>
        <meta property="fb:admins" content="'.$fb_admins.'"/>
        <meta property="og:type" content="article" />
        <meta property="og:url" content="'.$site_url.'/" />
        <meta property="og:image" content="'.$use_pic.'" />
        <meta property="og:site_name" content="'.$site_url_displayname.'" />
        <meta property="og:description" content="'.$use_text.'" />
        ';

        return $meta_string;

}


        // Meta Cases
        switch($page_title) {
            case "": case "home": 
                echo show_fbmeta_home();
                exit();
            break;
        }

        show_fbmeta_home();

Of course, the script would be extended for each link. If no function for the actual website is present, the home-page would be used.

Is this a legacy-style method, or, could this cause some problems in the future?

Answer 1

• It would be better to assign $page_path_display this value ("/") from the beginning as all the cases use that as a prefix.

• You're missing whitespace in this statement ($expl_path[2]!=""), it should be $expl_path[2] != "".

• In the following code block, you don't need to assign $meta_string as you return it straight away.

    return
    '<meta property="og:title" content="'.$use_title.'" />
    <meta property="fb:app_id" content="'.$fb_app_id.'"/>
    <meta property="fb:admins" content="'.$fb_admins.'"/>
    <meta property="og:type" content="article" />
    <meta property="og:url" content="'.$site_url.'/" />
    <meta property="og:image" content="'.$use_pic.'" />
    <meta property="og:site_name" content="'.$site_url_displayname.'" />
    <meta property="og:description" content="'.$use_text.'" />
    ';

• In the following code block, you could just use an if-else instead of a switch

    switch($page_title) {
        case "": case "home": 
            echo show_fbmeta_home();
            exit();
        break;
    }

for example:

if ($page_title == "" || $page_title == "home"){
    echo show_fbmeta_home();
    exit();
}

• global, you should avoid using globals, because they're bad practice.