PHP MySQLi num_rows始终返回0

Question

我已经构建了一个利用PHP内置MySQLi类功能的类,它旨在简化数据库交互.但是,使用OOP方法,在运行查询后,num_rows实例变量返回正确的行数时遇到困难.看看我班上的快照......

class Database {
//Connect to the database, all goes well ...

//Run a basic query on the database
  public function query($query) {
  //Run a query on the database an make sure is executed successfully
    try {
    //$this->connection->query uses MySQLi's built-in query method, not this one
      if ($result = $this->connection->query($query, MYSQLI_USE_RESULT)) {
        return $result;
      } else {
        $error = debug_backtrace();

        throw new Exception(/* A long error message is thrown here */);
      }
    } catch (Exception $e) {
      $this->connection->close();

      die($e->getMessage());
    }
  }

//More methods, nothing of interest ...
}

以下是一个示例用法:

$db = new Database();
$result = $db->query("SELECT * FROM `pages`"); //Contains at least one entry
echo $result->num_rows; //Returns "0"
exit;

怎么这不准确？结果对象中的其他值是准确的,例如"field_count".任何帮助是极大的赞赏.

感谢您的时间.

Answer 1

可能的错误:http://www.php.net/manual/en/mysqli-result.num-rows.php#104630

代码来自上面的来源(Johan Abildskov):

$sql = "valid select statement that yields results"; 
if($result = mysqli-connection->query($sql, MYSQLI_USE_RESULT)) 
{ 
          echo $result->num_rows; //zero 
          while($row = $result->fetch_row()) 
        { 
          echo $result->num_rows; //incrementing by one each time 
        } 
          echo $result->num_rows; // Finally the total count 
}

也可以使用Procedural样式进行验证:

/* determine number of rows result set */
$row_cnt = mysqli_num_rows($result);