Default value for return

A few days ago, i try to create a code with PHP, with a function i do a return in function with some values and then i got a mystery about default value for return keyword, to get absolutelly value with this keyword i create a function to test it, like this.

function defaultValueForReturn(){  
   return;  
}// now i test it

var_dump (defaultValueForReturn());  ?>

And this is result:


What about with other programming language such as Python, Javascript, etc.
Check this!

Python.
Code:

#!/usr/bin/env python  
def defaultValueForReturn():  
    return  
  
type(defaultValueForReturn())  

Result:


Javascript.
Code:

function returnValue() {  
   return;  
}  
  
var y = returnValue();  
console.log(typeof (y));  

Result:
undefined

Ruby.
Code:

def defaultValueForReturn()  
    return  
end  
  
y=defaultValueForReturn()  
print y.class  

Result:
NilClass