PHP was created by Rasmus Lerdorf. Sessions allow storing temporary data across HTTP requests to offer complete transactions to visitors. Variables can be passed between pages via registering in a session, cookies, or URLs. Arrays can be counted with count() or sized with sizeof(). The move_uploaded_file() function stores uploaded files. Constructors initialize objects and destructors cleanup when objects are destroyed. Constants are defined with define() and inheritance only allows single base classes in PHP.