PDOStatement::fetchObject()

(PHP 5 >= 5.1.0, PHP 7, PECL pdo >= 0.2.4)

获取下一行并作为一个对象返回。

说明

PDOStatement::fetchObject([string $class_name= "stdClass"[,array $ctor_args]]): mixed

获取下一行并作为一个对象返回。此函数（方法）是使用PDO::FETCH_CLASS或PDO::FETCH_OBJ风格的PDOStatement::fetch()的一种替代。

参数

$class_name

创建类的名称。

$ctor_args

此数组的元素被传递给构造函数。

返回值

返回一个属性名对应于列名的所要求类的实例，或者在失败时返回FALSE.

参见

• PDOStatement::fetch() 从结果集中获取下一行

Be warned of the rather unorthodox behavior of PDOStatement::fetchObject() which injects property-values BEFORE invoking the constructor - in other words, if your class initializes property-values to defaults in the constructor, you will be overwriting the values injected by fetchObject() !
A var_dump($this) in your __construct() method will reveal that property-values have been initialized prior to calling your constructor, so be careful.
For this reason, I strongly recommend hydrating your objects manually, after retrieving the data as an array, rather than trying to have PDO apply properties directly to your objects.
Clearly somebody thought they were being clever here - allowing you to access hydrated property-values from the constructor. Unfortunately, this is just not how OOP works - the constructor, by definition, is the first method called upon construction. 
If you need to initialize your objects after they have been constructed and hydrated, I suggest your model types implement an interface with an init() method, and you data access layer invoke this method (if implemented) after hydrating.

It should be mentioned that this method can set even non-public properties. It may sound strange but it can actually be very useful when creating an object based on mysql result.
Consider a User class:
<?php
class User {
  // Private properties
  private $id, $name;
  private function __construct () {}
  public static function load_by_id ($id) {
   $stmt = $pdo->prepare('SELECT id, name FROM users WHERE id=?');
   $stmt->execute([$id]);
   return $stmt->fetchObject(__CLASS__);
  }
  /* same method can be written with the "name" column/property */
}
$user = User::load_by_id(1);
var_dump($user);
?>
fetchObject() doesn't care about properties being public or not. It just passes the result to the object. Output is like:
object(User)#3 (2) {
 ["id":"User":private]=>
 string(1) "1"
 ["name":"User":private]=>
 string(10) "John Smith"
}

You can access MySQL tables in an objective way. Suppose you have a table named Users that has fields: UserID, UserName, UserPassword, UserBirthday, you can create a PHP class extending DataObject that is associated with this table:
<?php 
class User extends DataObject {
  // name: Table Name, key: Primary Key (can be an array), auto: AUTO_INCREMENT field
  protected static $_table = array('name' => 'Users', 'key' => 'UserID', 'auto' => 'UserID');
  // relationships between PHP properties and MySQL field names
  protected static $_propertyList = array('id' => 'UserID', 'name' => 'UserName', 'password' => 'UserPassword', 'birthday' => 'UserBirthday');
  
  // A method that fetches all users as an array
  public static function GetAll() {
    global $dbh;
    $sql = 'SELECT * FROM Users';
    $stmt = $dbh->query($sql);
    $users = array();
    while ($user = $stmt->fetchObject(__CLASS__)) {
      $users[] = $user;
    }
    return $users;
  }
  // Methods that fetch a specific user
  public static function GetUserByName($name) {}
  public static function GetUserByID($name) {}
  
  // Methods for the current user object
  public function checkPassword($password) {return $this->password == $password;}
  public function showLink() {return "<a href=\"user.php?i={$this->id}\">{$this->name}</a>";}
}
// Then, you can create an instance of this class to insert a row in your table
$user = new User();
$user->name = 'oct1158';
$user->password = '789012';
$user->useFunction('birthday', 'NOW()');
echo 'Field birthday uses MySQL Function: ', $user->birthday, '<br>';
if ($user->insert()) {
  echo 'New User ID: ', $user->id, '<br>';
  
  // Update the row
  $user->password = '112233';
  $user->update();
} else {
  echo 'INSERT Failed<br>';
}
// Get a specific user by a query
$sql = 'SELECT * FROM Users WHERE UserName = ?';
$stmt = $dbh->prepare($sql);
$stmt->execute(array('admin'));
$admin_user = $stmt->fetchObject('User');
echo 'Admin ID is ', $admin_user->id, '.<br>';
echo 'Admin Birthday is ', $admin_user->birthday, '.<br>';
// Get all users by a static method of that class
$users = User::GetAll();
echo '<br>';
echo $users[0]->name, ', ', $users[0]->birthday, '<br>';
echo $users[1]->name, ', ', $users[1]->birthday, '<br>';
echo $users[2]->name, ', ', $users[2]->birthday, '<br>';
echo '<br>';
// Create an empty user and then delete it immediately
$user = new User();
$user->insert();
$user->delete();
?>
The DataObject class example:
<?php 
class DataObject {
  private $changedFields = array(); // list of updated fields
  private $data = array(); // original row from PDOStatement
  private $funcFields = array(); // fields that use MySQL functions
  // The properties above are private in this class, so even if in your subclass you define some properties named the same, or you associate a property of the same name with a field in your table, they will never influence these properties.
  function __get($property) {
    if (isset($this::$_propertyList[$property])) {
      return $this->data[$this::$_propertyList[$property]]; // access fields by PHP properties
    } else {
      return $this->$property; // throw the default PHP error
    }
  }
  function __set($property, $value) {
    if (isset($this::$_propertyList[$property])) {
      $field = $this::$_propertyList[$property];
      $this->data[$field] = $value; // update $data
      
      // take down changed fields
      if (!in_array($field, $this->changedFields)) {
        array_push($this->changedFields, $field);
      }
      $index = array_search($field, $this->funcFields);
      if ($index !== false) {
        unset($this->funcFields[$index]);
        $this->funcFields = array_values($this->funcFields);
      }
    } else {
      // For fetchObject
      $this->data[$property] = $value; // redirect to Array $data
    }
  }
  private function checkPrimaryKey() {}
  private function clear() {}
  public function delete() {}
  public function insert() {}
  public function update() {}
  public function useFunction($property, $function) {}
}
?>

PDOStatement::fetchObject() injects values as string, I needed a conversion type.
I did it including settype() function in class constructor
Below method that find an user by id and return user object instance:
<?php
class UserMapper extends MapperAbstract
{
  //other code
  public function findById(int $userId)
  {
    $pdos = $this->dBase->prepare('SELECT user_id AS objectId, name, description, password, active, created, 
    last_update AS lastUpdate FROM user WHERE user_id = :id');
    $pdos->bindParam(':id', $userId, \PDO::PARAM_INT);
    $pdos->execute();
    return $pdos->fetchObject('\DomainObjects\User', array($this->password));
  }
  //other code
}
?>
User class with type handling:
<?php
class User extends DomainObjectAbstract
{
  //other code
  public function __construct(Password $password)
  {
    $this->passwordUtility = $password;
    
    settype($this->objectId, 'integer');
    settype($this->active, 'integer');
  }
  //other code
}
?>
var_dump() of returned User instance:
<?php
object(DomainObjects\User)[18]
 public 'name' => string 'root' (length=4)
 public 'description' => string 'System User' (length=11)
 public 'password' => string '$2y$11$4IAn6SRaB0osPz8afZC5D.CmTrBGxnb5FQEygPjDirK9SWE/u8YuO' (length=60)
 public 'active' => int 1
 public 'created' => string '2015-02-14 10:39:00' (length=19)
 public 'lastUpdate' => string '2016-08-30 18:46:56' (length=19)
 private 'passwordUtility' => 
  object(Auth\Password)[13]
   protected 'options' => 
    array (size=1)
     'cost' => int 11
 protected 'objectId' => int 1
?>
'objectId' and 'active' are now of the type required

If using a namespaced class, you must provide the fully qualified class name; fetchObject does not seem to know about any "use" statements.
This results in a PHP Fatal error: Class 'MyClass' not found...:
<?php
use MyNamespace\MyClass;
// ...
$o = $statement->fetchObject('MyClass'));
?>
This works:
<?php
use MyNamespace\MyClass; //still needed for my code
// ...
$o = $statement->fetchObject('MyNamespace\\MyClass'));
?>

I think so could us use this variant to implement the constructor, this is my example:
<?php
class User{
  public $user;
  public $password;
  public $name;
  public $email;
  
  public function __construct(){
    $args = func_get_args();
    $nargs = func_num_args();
    $attribs = get_class_vars(get_class($this));
    if(isset($args)){
      foreach($args as $value){
        $attrib = key($attribs);
        $this->$attrib = $value;
        next($attribs);
      }
    }
  }
}

Because of the injection of object properties before the constructor is executed, I usually build my classes like this to make sure already set properties aren't overwritten:
<?php
class Person {
 public $name;
 public $age;
 public $sex;
 public function __construct($name=NULL, $age=NULL, $sex=NULL) {
  $this->name = $name === NULL ? $this->name : $name;
  $this->age = $age === NULL ? $this->age : $age;
  $this->sex = $sex === NULL ? $this->sex : $sex;
 }
}
?>