PHP Fatal error: Cannot redeclare

If your browser saw an error message PHP Fatal error: Cannot redeclare function it is an issue with your code or script as it tries to declare the same function multiple times

It means the function is already defined  or the following can be the issue

1. Same function defined in two files.
2. Same function defined in two places within the same file.
3. the file where the function is defined is included two times (function defined 2 times)
   
   

You can use the include_once instead of include to include your functions.php file to overcome the issue you face in the above 3rd point.