(PECL runkit >= 0.7.0)
runkit_class_adopt — Convert a base class to an inherited class, add ancestral methods when appropriate
$classname
   , string $parentname
   )
classnameName of class to be adopted
parentnameParent class which child class is extending
   Returns TRUE on success or FALSE on failure.
  
Example #1 A runkit_class_adopt() example
<?php
class myParent {
  function parentFunc() {
    echo "Parent Function Output\n";
  }
}
class myChild {
}
runkit_class_adopt('myChild','myParent');
myChild::parentFunc();
?>
The above example will output:
Parent Function Output