PDO结果显示先前查询的结果，如何显示当前结果？

Question

I have two queries however the pdo->results are showing the original results and not the next results. I want results query_1 = (a1, a2, a3) and then query_2 = (b1, b2, b3). But the results are showing a1, a2, a3 and then a1, a2, a3 again.

DbGlobal.php:

class DbGlobal 
{
  private static $_instance = null;

  private $_pdo,
      $_query,
      $_error = false,
      $_results,
      $_count = 0;

  private function __construct()
  {
    try 
    {
        $this->_pdo = new PDO('mysql:host='. ConfigGlobal::get('mysql/host') .';dbname='. ConfigGlobal::get('mysql/db'), ConfigGlobal::get('mysql/username'), ConfigGlobal::get('mysql/password'));
        //$this->_pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    } 
    catch (PDOException $e) 
    {
        die($e->getMessage());
    }
  }

  public static function getInstance()
  {
    if(!isset(self::$_instance)) 
    {
        self::$_instance = new DbGlobal();
    }
    return self::$_instance;
  }

  public function query($sql, $params = array())
  {
    $this->_error = false;

    if($this->_query = $this->_pdo->prepare($sql)) 
    {
      $x = 1;
      if(count($params)) 
      {
        foreach($params as $param) 
        {
          $this->_query->bindValue($x, $param);
          $x++;
        }
      }
      if($this->_query->execute()) 
      {
        $this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);
        $this->_count = $this->_query->rowCount();
      } 
      else 
      {
        $this->_error = true;
      }
    }
    return $this;
  }
}

QueryPage_1.php

$varname = 'Settings_SideBarButtons';
$vararray = array("UniqueId,", "Url,", "Dirr,");
$varstring = implode($vararray);
${$varname} = DbGlobal::getInstance()->query("SELECT ".$varstring." FROM 
".$varname." WHERE a='1'");

In database:

UniqueId => a1
Url => a2
Dirr => a3

Results are correct:

print_r($Settings_SideBarButtons->results());
//output:
Array 
( [0] => stdClass Object 
    ( [UniqueId] => a1 
      [Url] => a2 
      [Dirr] => a3
    ) 
) 

And then I have in the same query script with another query that has a different varname.

QueryPage_2.php

$varname = 'Core_Settings';
$vararray = array("UniqueId,", "Url,", "Dirr,");
$varstring = implode($vararray);
${$varname} = DbGlobal::getInstance()->query("SELECT ".$varstring." FROM 
".$varname." WHERE a='1'");

In database:

UniqueId => b1
Url => b2
Dirr => b3

But the Results are:

print_r($Core_Settings->results());
//output:
Array 
( [0] => stdClass Object 
    ( [UniqueId] => a1 
      [Url] => a2 
      [Dirr] => a3
    ) 
) 

I have confirmed that the results displayed in the second query are the results from the first query.
Am I using PDO object incorrectly? Do I have to PDO->freeresult(); somehow?

Answer 1

Woops. Easy mistake: I had an extra database field in the second $vararray that was not present in the database. The PDO error wasn't printing because it had been commented out in my query statement class.

So remember to turn on error reporting guys.

Here's my PDO error fix to my code above:

private function __construct()
{
    try 
    {
        $this->_pdo = new PDO('mysql:host='. ConfigGlobal::get('mysql/host') .';dbname='. ConfigGlobal::get('mysql/db'), ConfigGlobal::get('mysql/username'), ConfigGlobal::get('mysql/password'));
        $this->_pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); //added this
    } 
    catch (PDOException $e) 
    {
        die($e->getMessage());
    }
}