Public static boolean property becomes false in __destruct

I have a class with a static public boolean property which is supposed 
to be false. It's set to false on initialization ("public static boolean 
$myvar = false;"), and overridden to false again in __construct. I've 
also dumped the value of the property in nearly every function in my 
application, and the value remains false.
However, when I actually check the property in a if in the class 
destructor, it evaluates to true. I've also set a breakpoint with 
xdebug, which shows the value of the property to be true at this point.
I've done a full search, and nowhere in my application should the value 
become true; the only place where it's modified is "MyClass::$myvar = 
false;" at one point.

Does anyone have any idea why the boolean property's value appears to be 
true in the __destruct, despite never being set to true?

Thank you in advance.