Support » Fixing WordPress » Fatal error:Call to undefined function wp_is_mobile

  • Resolved TinTeddy


    Sorry to have to ask, but I can’t get to my blog and am getting very stressed now. I am new to WordPress, please bear this in mind.

    When I try to access my wp-admin dashboard thing to update my blog I get an error message: Fatal error: Call to undefined function wp_is_mobile() in D:\Hosting\9251946\html\tinteddy\wordpressdir\wp-admin\index.php on line 22

    I update WordPress to the lateset version yesterday evening, I can only assume that is what has caused this.

    I have read a couple of posts and tried the following.

    I renamed the themes folder as MYTHEME-old – still get same error
    I renamed the plugins folder as plugins.hold – still same error

    Again, I am a beginner with all this code stuff. If anyone could please give me some information on how to edti my blog I would be so grateful, it means a lot to me.

Viewing 15 replies - 1 through 15 (of 21 total)
  • esmi


    Forum Moderator

    – switching to the Twenty Eleven theme by renaming your current theme’s folder inside wp-content/themes and adding “-old” to the end of the folder name using FTP or whatever file management application your host provides.

    resetting the plugins folder by FTP or phpMyAdmin.

    – re-uploading all files & folders – except the wp-content folder – from a fresh download of WordPress.

    – running the upgrade manually via wp-admin/upgrade.php

    I have done that, as said above.

    I think I have now solved it – I found the tmp file from the upgrade and used that to copy the files over. So now back where it was before upgrade – working!

    Thank you for your help anyway.

    having same issue on a few sites.



    Forum Moderator

    Please post your own topic.

    for me the problem plugin was “sitepress-multilingual-cms”… once i changed the name or deleted it up and running again.

    Had the same problem: Fatal error: Call to undefined function wp_is_mobile() in D:\Hosting\…

    Did ––> re-uploading all files & folders – except the wp-content folder – from a fresh download of WordPress.

    Working again now. Thank you esmi

    I still do not have a working copy of WordPress 🙁 It was partly working, but I couldn’t add tags or images without it complaining about missing files. So…

    I installed Filezilla. I took a fresh downloaded copy of WordPress 3.4.

    I copied the folders wp-admin and wp-includes into my host directory, on top of the old ones that were already there. I also copied the loose files that are in the wordpress main directory – in other words I copied everything except the wp-content folder, as suggested above.

    Now when I try to go into wordpress it tells me it needs to update the database. I click the Update Database button and get an error:

    Fatal error: Class ‘WP_Theme’ not found in D:\Hosting\9251946\html\tinteddy\wordpressdir\wp-includes\theme.php on line 106

    I tried renaming my theme as yoko-old. But this still happens.

    I have also renamed the plugins folder plugins.hold, as suggested.

    I still get the request to update database, then that error message.

    Is there any way to clear it, reinstall and then drop my blog posts back in?

    I feel hopelessly out of my depth and just want to be able to use my blog. Nothing technical, just basic posts 🙁



    Forum Moderator

    Delete the wp-admin & wp-includes folder as well as all files in your root folder with the exception of wp-config.php and your .htaccess file (if you have one). Then re-upload all files & folders – except the wp-content folder – from a fresh download of WordPress.

    Thank you, esmi, I am doing that now… (nervously)



    Forum Moderator

    As long as you stay away from the wp-content folder, you should be fine. I also recommend that people make backup copies of their wp-config.php and root .htaccess files for safekeeping – just in case they get a little carried away with the delete button.

    Yay, everything seems to be back to normal in my dashboard now. I see my posts etc. And no error messages.

    But my blog is not online. When I go to the address there is nothing at all.

    I backed up the whole thing before poking. I don’t seem to have had an .htaccess file. And I copied my old wp-config.php file over so using that.

    Oooh, i renamed the theme back to what it was.. and now i see my blog again!

    Thank you so much, esmi *hugs you like mad*



    Forum Moderator

    Glad I could help 🙂

Viewing 15 replies - 1 through 15 (of 21 total)
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