Answer 1

Answer 2

经过大量的网络搜索并阅读CakePHP的文档，这是我提出的解决方案：

    function unpaidClass($id) {
    $this->FeePayment->unbindModel(array(
        'belongsTo' => array('Student')
    ), $reset = 0);

    $this->FeePayment->bindModel(array(
        'belongsTo' => array(
            'Student' => array(
                'foreignKey' => false,
                'conditions' => array('Student.id = FeePayment.student_id')
            ),
            'YearGroup' => array(
                'foreignKey' => false,
                'conditions' => array('YearGroup.id = Student.year_group_id')
            )
        )
    ), $reset = 0);

    $this->paginate = array(
        'contain' => array('Student','YearGroup'),
        'conditions' => array('YearGroup.school_year' => $id, 
            'FeePayment.status' => 'Unpaid',
            'FeePayment.due_date <= ' => date("Y-m-d")));

    $this->set('feePayments', $this->paginate());
}