php实现判断访问来路是否为搜索引擎机器人的方法

private function getrobot()
{
 if (empty($_server['http_user_agent']))
 {
  return false;
 }
 $searchenginebot = array(
  'googlebot'=>'google',
  'mediapartners-google'=>'google',
  'baiduspider'=>'baidu',
  'msnbot'=>'msn',
  'yodaobot'=>'yodao',
  'youdaobot'=>'yodao',
  'yahoo! slurp'=>'yahoo',
  'yahoo! slurp china'=>'yahoo',
  'iaskspider'=>'iask',
  'sogou web spider'=>'sogou',
  'sogou push spider'=>'sogou',
  'sosospider'=>'soso',
  'spider'=>'other',
  'crawler'=>'other',
 );
 $spider = strtolower($_server['http_user_agent']);
 foreach ($searchenginebot as $key => $value)
 { 
  if (strpos($spider, $key)!== false)
  {
   return $value;
  }
 }
 return false;
}
public function isrobot()
{
 if($this->getrobot()!==false)
 {
  return true;
 }
 return false;
}