<?php

class Foo extends Bar {
  const FOOBAR = 'FOOBAR';

  public function baz() {
    echo Foo::FOOBAR;
    echo self::FOOBAR;
  }
}
~~~~~~~~~~
warning:7:10
~~~~~~~~~~
<?php

class Foo extends Bar {
  const FOOBAR = 'FOOBAR';

  public function baz() {
    echo self::FOOBAR;
    echo self::FOOBAR;
  }
}