After setting up Apache it's not serving PHP files, but showing the contents of the files instead

If you would stick to the tutorial/documentation this would not have happened:

https://wiki.invoiceplane.com/en/1.0/getting-started/installation

Hi @Love_Grover I saw the error output you pasted to just paste. If I understand right, your server is printing the whole index.php file, this is usually a problem that has to do with php not serving the file correctly. How is php installed on your server?