php - PDO::FETCH_CLASS，构造函数参数怎么写？

Question

我喜欢使用 PDO::FETCH_CLASS 来获取对象数组，应该调用构造函数，因为我需要此类中的构造函数。作为第三个参数，我使用数据库表中的列名。结果我得到了列的名称，但不是数据库中的预期值。我正在使用 mariaDB。

没有构造函数(并且只有 2 个参数)，我得到一个包含正确对象的数组。

 $dbh = Db::connect();
   $sql = 'SELECT * FROM dancer';
   $stmt = $dbh->prepare($sql);
   $stmt->execute();
   // additional "|PDO::FETCH_PROPS_LATE" in 1. argument ignores 
   // the constructor
   $dancers = $stmt->fetchAll(PDO::FETCH_CLASS
   ,"Dancer"
   ,array("firstName","lastName","id")
 );

预期结果:

  [0] => Dancer Object
    (
      [id:Dancer:private] => 7
      [firstName:Dancer:private] => Carl
      [lastName:Dancer:private] => Classen
    )

实际结果:

  [0] => Dancer Object
    (
      [id:Dancer:private] => id
      [firstName:Dancer:private] => firstName
      [lastName:Dancer:private] => lastName
    )

PHP 类

class Dancer
{
  private $id;
  private $firstName;
  private $lastName;

    public function __construct($firstName, $lastName, $id = null)
    {
      if (isset($id)){
        $this->id = $id;
      }
      $this->firstName = $firstName;
      $this->lastName = $lastName;
  }

    #GETTER AND SETTER

    public static function getAll()
      {
        try {
          $dbh = Db::connect();
          $sql = 'SELECT * FROM dancer';
          $stmt = $dbh->prepare($sql);
          $stmt->execute();

          $dancers = $stmt->fetchAll(PDO::FETCH_CLASS
            ,"Dancer"
            ,array("firstName","lastName","id")
          );
        } catch (PDOException $e) {
          print "Error!: " . $e->getMessage() . "<br/>";
          die();
        }
        return $dancers;
    }
}

Answer 1

自从我使用 FETCH_CLASS 以来已经有很长一段时间了，所以我花了一段时间才记住它们应该如何(？)结合在一起。我做了一个测试:

class foo{

    private $username;
    private $userid;


    public function __construct( $arg1, $arg2 ){
        /* assign "ctor_args" as named properties */
        $this->username=$this->$arg1;
        $this->userid=$this->$arg2;

        /* do something with the newly created properties */
        $this->render( $arg1, $arg2 );
    }
    private function render( $arg1, $arg2 ){
        printf('
        <pre>
            username: %s
            userid: %s
        </pre>',
        $this->username,
        $this->userid
        );
    }
}


$ctor_args=array( 'name', 'uid' );


/* 
    use aliases to modify column names to 
    indicate the assignment within the class 
    later
*/
$sql='select `username` as `name`, `userid` as `uid` from users';
$stmt=$db->prepare( $sql );
$res=$stmt->execute();


/* fetch results - calling the `foo` class with additional `ctor_args` */
$stmt->fetchAll( PDO::FETCH_CLASS, 'foo', $ctor_args );

此输出(表中只有 2 行)

username: RamRaider
userid: d6ba0682d75eb986237fb6b594f8a31f

username: Dustybin
userid: FHsdf44dfsdfcvhbfgh86237fb6b594f8a31f

所以也许如果你将构造函数方法更改为

public function __construct($firstName, $lastName, $id = null){
    if( isset( $this->$id ) ){
        $this->id = $this->$id;
    }
    $this->firstName = $this->$firstName;
    $this->lastName = $this->$lastName;
}