These classes are defined in the standard set of functions included in the PHP build. The class from which dir() is instantiated. These classes are defined in the Ming extension, and will only be available when that extension has either been compiled into PHP or dynamically loaded at runtime. These classes are defined in the Oracle 8 extension, and will only be available when that extension has either been compiled into PHP or dynamically loaded at runtime. These classes are defined in the qtdom extension, and will only be available when that extension has either been compiled into PHP or dynamically loaded at runtime.