Google Maps Plugin Can't Activate: Call to undefined function is_multisite()


I just became a subscriber today and was a little disappointed when I could activate this plugin. I'm sure it's because I'm running an older version of WordPress, 2.8.5 that's causing the issue. I'm just hoping there is a workaround as I am unable to upgrade this blog in particular because the developer before me hacked core. Upgrading will break the site beyond use.

I really need to get this plugin working asap as no other plugin available on seems to do what I need it to do where this plugin does. If that means hacking this plugin to work, so be it, regardless if I won't be able to update it or not. That might sound like a bad stance to have but this site sucks and I've just gotta get it working. While I would like to, I don't have time to rebuild this site properly. They just want this mapping functionality added to the site.


  • Philip John
    • DEV MAN’s Apprentice


    Unfortunately it's likely that it is because you're using the old version. It could also be a result of those core hacks though.

    Here's what you could do....
    1. Download a copy of your WordPress installation
    2. Download the latest version of WordPress
    3. Use a tool like DiffMerge to compare the two, showing up the differences
    4. Merge the two into a third copy of WordPress
    5. Create a test install using this third copy, importing the content from your existing site to see if the merge has been successful.

    Honestly, you need to do this at some point. 6, 12, 24 months down the line you'll find more and more plugins are incompatible which means that you'll have to turn to custom development for everything you want to do, and that'll be costly!

    Really, you need to find a developer now (try the jobs board) who can convert those core edits into custom plugins and upgrade your installation to future proof it.

    Sorry I can't provide anything more appealing!


  • interworks
    • New Recruit

    Hi Phil,

    Thanks for the reply but like my OP said I don't have time to upgrade the WordPress core. I'm a developer and it's a matter of billable time. The client won't spend the time/money to perform the upgrades at this time that's why I was asking for a workaround. This site has sat stagnant for nearly two years now and they just want to add this functionality to it and then it will sit for another 2+ years.

    Any other ideas would be great.


  • Mason
    • DEV MAN’s Sidekick

    Actually, I'm not aware of a similar call that was available in WPMU:

    However, you may just be able to remove that check from this plugin (they wouldn't be able to update the plugin in the future - but that doesn't seem to be a concern at this point anyway :smiley:)

    Just make sure the plugin is in the plugins directory (as opposed to mu-plugins) and remove the following from line 42 of wpmu_dev_maps_plugin.php:
    is_multisite() && defined('WPMU_PLUGIN_URL') &&

    So that line 42 now looks like this:
    if (defined('WPMU_PLUGIN_DIR') && file_exists(WPMU_PLUGIN_DIR . '/' . basename(__FILE__))) {

    That should do the trick. I tested it - but not on an older install. There could be a myriad of other conflicts that'll come up. Best of luck though!


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