怎么得到return的值，

		public function huancheng($key)
		{
             $key="永兴村到山水人家";
             $str="";
		     $keys=explode('到',$key);
             $json = @file_get_contents("http://api.map.baidu.com/direction/v1?mode=transit&origin=".$keys[0]."&destination=".$keys[1]."®ion=舟山&output=json&ak=gfPnxaaiPyNIhM7c3eZ1kmEL");
             $ar = json_decode($json,true);
             array_walk_recursive($ar, 'funv');
             function funv($v, $k) 
			 {
			   global $str;
               if($k == 'stepInstruction') 
			   {$str.= strip_tags($v);} 
			 }
			 return $str;	
         }