You are writing a PHP script and you need to use a callback function. How would you do this?

In PHP, to use a callback function in a script, you can pass the callback function as an argument to another function, assign an anonymous function to a variable and use it as a callback, or define a named function and use it as a callback. All of the mentioned options are valid approaches to using a callback function in PHP. The choice depends on the specific requirements and context of the script. For further details, refer to the PHP documentation on callback functions: http://php.net/manual/en/language.types.callable.php