Description:
------------
Reflection`s 'getDocComment()' method only works at first time after a file was modified. The under code 

Reproduce code:
---------------
<?php
class abc{
        /**
         * abc
         *
         * @param integer $a
         * @return string
         */
        public function gete($a){
                return $b;
        }
}
$obj = new ReflectionMethod("abc",'gete');
echo $obj->getDocComment();

Expected result:
----------------
/**
 * abc
 *
 * @param integer $a
 * @return string
 */

on each running.

Actual result:
--------------
got right output only at first time run, and got 'false' when run again.