The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.
runkit_import() flag indicating
that class constants should be imported from the
specified file. Note that this flag is only meaningful
in PHP versions 5.1.0 and above.
runkit_import() flag indicating that
if any of the imported functions, methods, constants,
or properties already exist, they should be replaced with
the new definitions. If this flag is not set, then any
imported definitions which already exist will be discarded.