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
This point can be fixed easily by using include_once instead of include when including your PHP file.