Title: Fatal Error – Undefined Function
Last modified: August 21, 2016

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# Fatal Error – Undefined Function

 *  Resolved [Jason G.](https://wordpress.org/support/users/jggeorgebellsouthnet/)
 * (@jggeorgebellsouthnet)
 * [12 years, 9 months ago](https://wordpress.org/support/topic/fatal-error-undefined-function-3/)
 * Has anyone seen an issue with updating to the newest version (3.0.8) of the Customizr
   theme. It has worked great up until now. When updating from version 3.0.7 to 
   3.0.8, I am seeing a **Fatal Error – Call to Undefined Function tc__f()** in 
   index.php file. This only happens when activating the child theme. The parent
   works fine. I also see the issue even with all of my plugins deactivated. Have
   not been able to find anything on this so far. Any suggestions on how to resolve
   are appreciated! Thanks!

Viewing 3 replies - 1 through 3 (of 3 total)

 *  [ElectricFeet](https://wordpress.org/support/users/electricfeet/)
 * (@electricfeet)
 * [12 years, 9 months ago](https://wordpress.org/support/topic/fatal-error-undefined-function-3/#post-4027473)
 * There have been various re-shuffles of code templates over the last few releases.
   I suspect you have a php in your child theme that is calling a function that 
   no longer exists. Go through your altered functions one by one, commenting them
   out and then un-commenting one by one, to find the culprit.
 *  Thread Starter [Jason G.](https://wordpress.org/support/users/jggeorgebellsouthnet/)
 * (@jggeorgebellsouthnet)
 * [12 years, 9 months ago](https://wordpress.org/support/topic/fatal-error-undefined-function-3/#post-4027481)
 * Thank you ElectricFeet. I will take a look at the functions and see if I can 
   find the function causing the issue. I will update the post with more information
   once I have had a chance to review. Thanks again for your help!
 *  Thread Starter [Jason G.](https://wordpress.org/support/users/jggeorgebellsouthnet/)
 * (@jggeorgebellsouthnet)
 * [12 years, 9 months ago](https://wordpress.org/support/topic/fatal-error-undefined-function-3/#post-4027513)
 * Ok, it is working great now with the child theme active. I copied everything 
   from the parent folder into a child folder, then added my custom functions and
   CSS styles to the functions php and style.css files, respectively. I left everything
   in these files from the parent. Not sure why, but it would seem that the Child
   theme needed to have the ‘tc__f’ function in it. I thought if the function is
   in the parent, it would be enough. I have seen issues when duplicating functions
   before (repeating the same function in the child). Oh well, just glad it is now
   working! Thanks again, ElectricFeet.

Viewing 3 replies - 1 through 3 (of 3 total)

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## Tags

 * [fatal error](https://wordpress.org/support/topic-tag/fatal-error/)
 * [undefined function](https://wordpress.org/support/topic-tag/undefined-function/)

 * 3 replies
 * 2 participants
 * Last reply from: [Jason G.](https://wordpress.org/support/users/jggeorgebellsouthnet/)
 * Last activity: [12 years, 9 months ago](https://wordpress.org/support/topic/fatal-error-undefined-function-3/#post-4027513)
 * Status: resolved