How can PHP errors like "Call to undefined function" be resolved in a forum setup?

To resolve PHP errors like "Call to undefined function" in a forum setup, you need to make sure that the function being called is defined and accessible within the scope where it is being called. This can be achieved by including the file that contains the function definition before calling the function.

// Include the file that contains the function definition
include 'functions.php';

// Call the function that was previously undefined
myFunction();