How do you include php file in drupal page callback?

In Drupal, you can include a PHP file in a page callback by using the include or require statement within your custom page callback function. First, define the callback function in your module, and then use the include statement to include the desired PHP file. Make sure the file path is correct and accessible. Finally, register the page callback in your module's hook_menu or routing system, depending on the Drupal version you are using.