怎么样通过PHP使用反射机制实现查找类？

//参数1是类名,参数2是方法名
$func = new ReflectionMethod('UnifiedOrder_pub', 'getPrepayId');
//从第几行开始
$start = $func->getStartLine() - 1;
//从第几行结束
$end = $func->getEndLine() - 1;
//获取路径地址
$filename = $func->getFileName();

<?php
function a() {
}
class b {
 public function f() {
 }
}
function function_dump($funcname) {
 try {
  if(is_array($funcname)) {
   $func = new ReflectionMethod($funcname[0], $funcname[1]);
   $funcname = $funcname[1];
  } else {
   //这个应该是当只有一个参数的时候就看做是本类的发放吧,大概,自行百度
   $func = new ReflectionFunction($funcname);
  }
 } catch (ReflectionException $e) {
  echo $e->getMessage();
  return;
 }
 $start = $func->getStartLine() - 1;
 $end = $func->getEndLine() - 1;
 $filename = $func->getFileName();
 echo "function $funcname defined by $filename($start - $end)\n";
}
function_dump('a');
function_dump(array('b', 'f'));
$b = new b();
function_dump(array($b, 'f'));
?>