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

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

创建类的名称。

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:

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:

The DataObject class example: 

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:

User class with type handling:

var_dump() of returned User instance:

'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...:

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