PDO 将 lastInsertId() 返回为零 (0)，我不明白？

Question

This is my code ? PDO return always the last inserted id as 0, I tried everything.!

$this->db()->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "INSERT INTO inbox (sender,recever) VALUES ('1','2')";
$this->db()->exec($sql);        
$project_id =$this->db()->lastInsertId();

The sql code table :

CREATE TABLE inbox(
id int(10) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
sender int,
recever int
);

Answer 1

Try this

//set persistent connection
$con = new PDO("mysql:host=$this->host;dbname=$this->dbname",$this->use‌​r,$this->pass,array(‌​PDO::ATTR_PERSISTENT => TRUE));    
$stmt = $con->prepare("INSERT INTO inbox (sender,recever) VALUES ('1','2')");
$stmt->execute();
$id = $db->lastInsertId();

Answer 2

The problem is your db() method which creates a new connection every time it is called.

Instead of such method, use a property. Assign your PDO instance to $this->db property and then use it whenever you need a PDO connection.

While your current implementation is just terrible, and workaround you have been offered in the other answer is not guaranteed to work. Let alone it shouldn't be used in the first place.