Description:
------------
Within only __set(), you can set a value of a new property with an empty name ($p = null; $this->$p = 1;).  The property won't really be created though - the effects will be invisible to the user.  No errors, warnings, or notices are generated.  This lack of an error message might cause difficult to pinpoint bugs since all assignments of previously undeclared properties within object scope regardless of originating method are routed through __set();

Elsewhere in the object, attempting this will cause a fatal 'Cannot access empty property' error as expected.

Test script:
---------------
<?php

class A{

	function __set($prop, $val) {
		echo "SET $prop = $val\n";
		$this->$prop = $val; // should've caused error
		}

	}

$a = new A();
$prop = null;

$a->$prop = 2;

print_r($a); // empty object

?>

Expected result:
----------------
fatal 'Cannot set empty property' or 'invalid property name' error.

Actual result:
--------------
Nothing.