In the PHP manual, to show the syntax for functions with optional parameters, they use brackets around each set of dependent optional parameter. For example, for the date() function, the manual reads:
string date ( string $format [, int $timestamp = time() ] )
Where $timestamp is an optional parameter, and when left blank it defaults to the time() function's return value.
How do you go about creating optional parameters like this when defining a custom function in PHP?