In case you ever encounter this exact or similar error "PHP Fatal error: Cannot redeclare function", it means that your script is trying to declare the same function multiple times.
This means one of the following things:
The function is defined in two separate files
The function is defined in two places in the same file
For these two cases, check the full error message: it will tell you in which file this function was previously declared.
The file in which you defined your function is included two times