Adding to 'lmfe at mega dot ist dot utl dot pt' contribution below, I have to say that this behaviour is very usual for PHP if MemberVars of an Object arent initialized from the constructor.
What worked best for me so far was something like this:
<?php
class foo {
var $bar
// the constructor
function foo() {
unset($this->bar); // with every instanciation, the variable is cleared for the object
}
}
?>