如何在PHP类中声明静态变量，但在扩展基类的类中定义它？

I'm have a DatabaseObject Class that has select, insert, update and delete methods defined. The purpose of the class is to represent a subset of rows in my MySQL database as a PHP object. The constructor calls MySQL's SELECT command and the destructor calls the DELETE command (unless I ask it not to).I'm have a DatabaseObject Class that has select