Expand php pdo to support impala, but the setAttribute() function failed

Question

Expand php pdo to support impala, but the setAttribute() function failed. My code is:

class ImpalaPDO extends PDO {

    public function __construct($dsn, $username, $passwd, $options)
    {
        parent::__construct($dsn, $username, $passwd, $options);
        $impala = new ImpalaPDOStatement();
        $impala->test();
        $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('ImpalaPDOStatement', array($this)));
    }
}

class ImpalaPDOStatement extends PDOStatement {

    public function test() {
        print "aaa";
    }
}

The error message is: SQLSTATE[HY000]: General error: PDO::ATTR_STATEMENT_CLASS requires format array(classname, array(ctor_args)); the classname must be a string specifying an existing class. What I can confirm is ImpalaPDOStatement is existing, because $impala->test() print a string successfully. So I don't know what the error message mean.

Answer 1

You must override protected constructor of PDOStatement:

class ImpalaPDOStatement extends PDOStatement {
    public $dbh;

    // Constructor must be overrided
    protected function __construct($dbh) {
        $this->dbh = $dbh;
    }

    public function test() {
        print "aaa";
    }
}