return 和echo的区别

$key="永兴村到山水人家";$str="";		     $keys=explode('到',$key);             $json = @file_get_contents("http://api.map.baidu.com/direction/v1?mode=transit&origin=".$keys[0]."&destination=".$keys[1]."&region=北京&output=json&ak=gfPnxaaiPyNIhM7c13eZ1kmEL");             $ar = json_decode($json,true);             array_walk_recursive($ar, 'funv');             function funv($v, $k) 			 {			   global $str;               if($k == 'stepInstruction') 			   {$str.= strip_tags($v);} 			   			 }			 return $str;

		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]."&region=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;			 }			 $str=funv($v,$k);			 return $str;				         }