PHP的可變call_user_func不工作

Question

我嘗試動態調用對象的方法，但沒有得到它的工作

the not working case 
$method = 'my_function'; 
$target_xml = call_user_func(array($api, $method)); 

Warning: call_user_func() expects parameter 1 to be a valid callback, second array member is not a valid method 

，如果我的var_dump（陣列（$ API，$法））

array (size=2) 
    0 => 
    object(APIModel)[12] 
     private 'client' => null 
     private 'affiliate' => null 
     private 'prod_category' => null 
     protected 'viewModel' => 
     object(ViewModel)[13] 
     protected 'db' => 
     object(MysqliDb)[14] 
      protected '_mysqli' => 
      object(mysqli)[15] 
       public 'affected_rows' => null 
       public 'client_info' => null 
       public 'client_version' => null 
       public 'connect_errno' => null 
       public 'connect_error' => null 
       public 'errno' => null 
       public 'error' => null 
       public 'error_list' => null 
       public 'field_count' => null 
       public 'host_info' => null 
       public 'info' => null 
       public 'insert_id' => null 
       public 'server_info' => null 
       public 'server_version' => null 
       public 'stat' => null 
       public 'sqlstate' => null 
       public 'protocol_version' => null 
       public 'thread_id' => null 
       public 'warning_count' => null 
      protected '_query' => null 
      protected '_join' => 
      array (size=0) 
       empty 
      protected '_where' => 
      array (size=0) 
       empty 
      protected '_whereTypeList' => null 
      protected '_orderBy' => 
      array (size=0) 
       empty 
      protected '_groupBy' => 
      array (size=0) 
       empty 
      protected '_paramTypeList' => null 
      protected '_bindParams' => 
      array (size=1) 
       0 => string '' (length=0) 
    1 => 
    object(SimpleXMLElement)[16] 
     string 'my_function' (length=5) 

工作情況

$target_xml = call_user_func(array($api, 'my_function')); 

Answer 1

正確使用：

$target_xml = call_user_func('my_function', array($api));