What are the best practices for naming PHP files and functions to avoid errors in include or require statements?

When naming PHP files and functions, it is important to follow certain best practices to avoid errors in include or require statements. One common issue is when the file name does not match the function name it contains, which can lead to errors when including or requiring the file. To avoid this, it is recommended to name the PHP file the same as the main function it contains, making it easier to include or require the file without confusion. Example PHP code snippet:

// File name: my_function.php
// Function name: my_function

function my_function() {
  // Function implementation
}
```

To include or require the file in another PHP script:

```php
include 'my_function.php';

my_function();