Description:
------------
The keys in the array returned by get_class_vars() contains NULLs if the field (or variable) is protected or private.
A more exact description of the syntax of the keys is listed below.
protected: "\x00*\x00<fieldname>"
private: "\x00<classname>\x00<fieldname>"
public: "<fieldname>"

Ok, it's a way to determine the access modifiers of the fields, but as the strings starts with NULL, most PHP functions will think the string is empty as it begins with a null (null-terminated strings). Example is preg_match().
In any case, get_class_vars() isn't supposed to do this kind of work; so any hint of the access shouldn't be included.

BTW, is get_class_vars() supposed to only return public fields? As the docs doesn't mentions it, I've assumed not.

Reproduce code:
---------------
<?php
class MyClass {
  protected $AProtectedField = "orange";
  private $APrivateField = "apple";
  public $APublicField = "strawberry";
}

$fields = get_class_vars('MyClass');
foreach($fields as $name => $value) {
 echo "$name : $value\n";
} 
?>

Expected result:
----------------
AProtectedField : orange
APrivateField : apple
APublicField : strawberry

Actual result:
--------------
\x00*\x00AProtectedField : orange
\x00MyClass\x00APrivateField : apple
APublicField : strawberry