How to get auto-increment Primary key of inserted row PDO PHP?

I want to insert a new row to a database using PDO in PHP, the primary key is auto-increment, so I am not inserting the value of the PK. This is the code:

public function insertQuestion($text){
    try{
        $sql = "INSERT INTO question(text) VALUES(:question)"; 

        $stm = $this->prepare($sql);

        $stm->execute(array(
                ':question' => $text,
        ));

        $question = new Question();
        $question->text = $text;
        $question->id = -1; // How do I get the PK of the row just inserted?

    }catch(PDOException $e){
        if ($e->getCode() == 1062) return FALSE; // fails unique constraint
        else echo $e->getMessage();
    }   
}

But, I need to store the PK of the new row inserted to the $question object, I have other attributes that are UNIQUE, so I could do a SELECT statement to find the PK, however, is there a better approach for doing it?