Silly OOP question

I've always wondered this about OOP and maybe you guys can answer this question. I'm writing a php application and I'm trying to figure out the correct way to right the oop part of this application. for instance. I have a "project.class" file that has functions for dealing with individual projects because you break down ideas into singular entities in OOP(as I understand it) But what if I wanted to deal with multiple projects such as getting a list of the projects in my database, should I create a function in the "project.class" to handle the now plural request, or should I create a "projects.class" file that has a function called "getProjects". Hopefully I'm explaining this question right. It makes sense in my own head. :-) Thanks, Brent