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Detecting and Redirecting Mobile Devices

   December 16th, 2010 Brian Herzog

Mobile website mockup in testiphone.comRemember a few months ago, when I was inspired by Steve Butzel's presentation at NELA2010 and created a mobile version of my library's website? I bet you have that date marked on your calendar.

Anyway, one lingering problem I had was some mechanism to automatically detect mobile devices when they visited our website, and reroute them to the mobile version instead of the full web version. I finally had some time this week and was able to accomplish that - aided by the fact that it was easier than I expected.

The ultimate goal is to redesign our entire site along the lines Brett suggested, by creating a stylesheet specifically for mobile devices. Brad pointed out that the Canton Public Library employs this, awesomely: visit their site and slowly make your browser window smaller, and watch the website flip from "full web" mode to "mobile" mode.

That was more than I could handle this week, so I opted for the detect-and-redirect approach. I had found online instructions using both javascript and php, and I went with the php method because

  • I think php is more reliable than javascript, because javascript depends on the browser whereas php runs on our server
  • Php is more fun, and I know our server runs php

The website offering the php method is http://detectmobilebrowsers.mobi, and very happily they make it available free for non-profits. Here's what I did:

  1. Read and reread their website
  2. Downloaded the main bit of code, and uploaded it to our web server
  3. Used their Function Generator to create the snippet of code to paste into the top of our homepage. I chose to treat all of their options as a mobile browser, and redirect them to http://www.chelmsfordlibrary.org/mobile - the resulting code looked like this:
    require_once('mobile_device_detect.php');
    mobile_device_detect(true,true,true,true,true,true,true,
    'http://www.chelmsfordlibrary.org/mobile',false);
    

    (this should be two lines of code, but it wraps because of the width of my blog - if you use this code, make sure the second and third lines above are actually one long line)

  4. I copy/pasted that code into our index.html homepage. However, because this is php code, it had to go between php tags, (<?php and ?>), so the complete code I actually added to the top of our page was:
    <?php 
    require_once('mobile_device_detect.php');
    mobile_device_detect(true,true,true,true,true,true,true,
    'http://www.chelmsfordlibrary.org/mobile',false);
    ?>
    

    (again, see note above about line wrapping)

  5. Note that the path in the "require_once" line must match where on your web server you actually saved the mobile_device_detect.php file (downloaded in Step 2)
  6. Now, the last step was a little tricky, because it involves editing the .htaccess on the server. It's easy though, and one of their faq answers explains it.

    Basically, .html files don't normally run php code - .php files do that. So if our homepage was index.php instead of index.html, I could have skipped this step. Instead, in order to make .html pages execute php, I had to add a few lines to our server's .htaccess file - which was no trouble at all - and then everything worked splendidly

That is, at least, so far. I've done some testing with mobile devices and (as suggested) with the User Agent Switcher Firefox add-on, and all of that has worked. But please, if you have a mobile device, visit our homepage (http://www.chelmsfordlibrary.org) and let me know if you don't get redirected to our mobile site.

A couple other notes:

  • I also added a link to the mobile site in the upper-left corner of the homepage, in case the redirect doesn't work
  • I only added this auto-detect to the homepage. I thought about adding it to every page, but our full site has a lot of information our mobile site doesn't - especially descriptions of our events. If I added the redirect to every single page, people with mobile devices basically wouldn't have access to any of that. So, my thinking is to provide mobile users with the (robust) basics, but if they want more than that they'll have to endure our not-great coding until we're able to redesign the entire site to be mobile-friendly

This was easier than I was expecting, which makes me think I missed something.

Update: someone pointed out a gap in my logic. On the mobile site, there is a link to "Visit our main site" which linked back to our full homepage. However, since the homepage redirected people to the mobile site, anyone clicking that link from the mobile site just got looped right back to the mobile site. So, I changed that link to go to our About page. Again, this is a good reason to just have mobile-friendly stylesheets like Brett and Brad suggest above.



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