How do you create optional arguments in php?

Question

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()

Answer 1

Some notes that I also found useful:

• Keep your default values on the right side.

  function whatever($var1, $var2, $var3="constant", $var4="another")
  

• The default value of the argument must be a constant expression. It can't be a variable or a function call.