undefined function wp_is_mobile() – How I Resolved This WP Issue?

After i have updated to new wordpress i.e. WordPress 3.4, i noticed a message that the attempt to update was failure. I didn’t pay much attention since i was comfortable with the present wordpress version also.

But soon after i logged out, and tried to login in to my admin area another time, it showed me an error message. But the actual site is running. I thought some problem in the login only. The wordpress error read like this:

Fatal error: Call to undefined function wp_is_mobile() in /home/onlinein/public_html/wp-login.php on line 67

I don’t have much technical knowledge about php or any other such thing, but i need to login to my admin area and dashboard. I didn’t know what to do… I searched online about this problem and found that many people are facing this problem from just recently. also, i noticed that most of the people facing this problem.

Now what i did is i logged in to my server page (cpanel) and i have opened file manager. Here I have opened login.php page since the problem is with login only. I opened this page, and removed whatever is present in 67 line. Then i refreshed the page, it showed error is present on 68 line. then i removed that one also. Now it is telling that the error is in 128 line. Now i understood that an element is present from 67 to 128 line in my login.php file of wp and hence it is preventing the login page by creating fatal error. I decided to try an idea. I removed the matter present from 67 to 128.

I tried to login now. The login page is now opening and i am able to login to my admin and dashboard succesfully. but there is slight difference in the look of login page now. I don’t know why.

Note: This is just my experience, and I don’t encourage anyone to do like this. It might result in loss of any code or page or may cause any other consequence. I don’t take any responsibility for that. You need to take your own risk in trying this way. All the best….