For interfaces and traits :<?phpinterface TestInterface { }trait TestTrait { }$interfaceClass = new ReflectionClass('TestInterface');$traitClass = new ReflectionClass('TestTrait');var_dump($interfaceClass->isAbstract());var_dump($traitClass->isAbstract());?>Using PHP versions 5.4- to 5.6, the above example will output:bool(false)bool(true)Using PHP versions 7.0+, the above example will output:bool(false)bool(false)