Methods that are intended to be called statically should be
$foo =& new Foo() construct should
not be used
instanceof operator should be used instead of
Declarations of methods in child classes should be compatible with those in parent classes
These changes obviously imply following the Error Handling Guidelines for PHP5
packages since PEAR class itself is not
Also the new object model should be taken into account: this means removing unneded references when working with objects and using clone where needed.