Added null references doc

Author: C-Stevens

doc/null-references

@@ -0,0 +1,33 @@
+[<-- Return to index](../README.md)
+# Null/Nil References
+
+### What does the language call these?
+#### PHP
+PHP calls variables with no value [`NULL`s](https://secure.php.net/manual/en/language.types.null.php). Variables are NULL if they are manually assigned as such, their value has never been set to anything before, or they are unset via the [`unset()`](https://secure.php.net/manual/en/function.unset.php) method.
+#### Python
+Python calls variables with no value `None`. 
+
+### What are the features of handling these?
+#### PHP
+Variables can be unset via the [`unset()`](https://secure.php.net/manual/en/function.unset.php) method and will become NULL.
+
+Variables can be checked against null via the [`is_null()`](https://secure.php.net/manual/en/function.is-null.php) method.
+#### Python
+In Python, `None` is actually an object, and behaves like one. Under the hood, `None` is of type `NoneType`. Variables can be checked against None programmatically just like any other object comparison:
+```python
+class myClass:
+    def __init__(self, foo, bar):
+        self.foo = foo
+        self.bar = bar
+
+a = myClass("apples", "oranges")
+b = None
+
+print("a is not None") if (a is not None) else print("a is None")
+print("b is not None") if (b is not None) else print("b is None")
+```
+Will yield:
+```
+a is not None
+b is None
+```