如何在MVC模式中重构我的模型类，这样我就不会反复使用每种方法进行准备和查询？

Is there a way to refactor this? The plumbing has to be put in somewhere:

Here is my index.php page:

define('BASE_URL', __DIR__);
echo BASE_URL;
require_once(BASE_URL . DIRECTORY_SEPARATOR . "config\\config.php");
require_once(BASE_URL . DIRECTORY_SEPARATOR . "Classes\\PdoAdapter.class.php");
require_once(BASE_URL . DIRECTORY_SEPARATOR . "Classes\\Student.class.php");

$adapter = new PdoAdapter(DB_DSN, DB_USER_NAME, DB_PASSWORD);
    $student = new Student($adapter);
    $student->findByStudentID(4);

Here are my classes:

require_once(BASE_URL . DIRECTORY_SEPARATOR . "Classes\\IStudent.interface.php");
class Student implements IStudent {

     public function __construct(IRepository $adapter) {
        $this->adapter = $adapter;
    }

    public function findByStudentID($id){
        $sql = 'SELECT * FROM students WHERE student_id = :student_id';
        $this->adapter->connect();
        $this->adapter->prepare($sql);
        $place_holders = array(':student_id' => $id);
        $this->adapter->execute($place_holders);
        $results = $this->adapter->fetchAll();
        //print_r($results);
        foreach ($results as $student){
            echo "</br>" . $student["student_id"] . " , " . $student["LAST"] . "</br>";

        }


        $this->adapter->disconnect();
        echo $sql;

    }

}

If I add a new method (same class), say:

require_once(BASE_URL . DIRECTORY_SEPARATOR . "Classes\\IStudent.interface.php");
class Student implements IStudent {

     public function __construct(IRepository $adapter) {
        $this->adapter = $adapter;
    }

    public function findByLastName($last_name){
        $sql = 'SELECT * FROM students WHERE LAST = :last_name';
        $this->adapter->connect();
        $this->adapter->prepare($sql);
        $place_holders = array(':last_name' => $last_name);
        $this->adapter->execute($place_holders);
        $results = $this->adapter->fetchAll();
        //print_r($results);
        foreach ($results as $student){
            echo "</br>" . $student["student_id"] . " , " . $student["LAST"] . "</br>";

        }


        $this->adapter->disconnect();
        echo $sql;

    }

}

Should I be doing the connect, prepare, execute, over and over in the model like this? I could be a mapper and this would create an ORM of sorts. But I really don't want an ORM. I have to do this somewhere. The model seemed to give me a lot of flexibility, but doesn't this tie me to PDO (which is okay with me).

This is using PHP 5.4, PDO with MySQL. The $adapter is a wrapper for a PDO class I have.

EDIT: I am using the concepts Model, Database, and Tables in a loose sense. I do not believe the Model is a table, for example. It is one aspect of the "M."

EDIT: I changed this:

 public function __construct(IRepository $adapter) {
    $this->adapter = $adapter;
    $this->adapter->connect();
}

Then in my calling page:

$adapter = new PdoAdapter(DB_DSN, DB_USER_NAME, DB_PASSWORD);

$student = new Student($adapter);
$student->findByStudentID(4);
$student->findByStudentLastName('Smith');

I think that is better. I also removed the disconnect() because I thought PDO automatically disconnected after the script is finished.

I now have:

<?PHP
require_once(BASE_URL . DIRECTORY_SEPARATOR . "Classes\\IStudent.interface.php");
class Student implements IStudent {

     public function __construct(IRepository $adapter) {
        $this->adapter = $adapter;
        $this->adapter->connect();
    }

    public function findByStudentID($id){
        $sql = 'SELECT * FROM students WHERE student_id = :student_id';
        $this->adapter->prepare($sql);
        $place_holders = array(':student_id' => $id);
        $this->adapter->execute($place_holders);
        $results = $this->adapter->fetchAll();
        //print_r($results);
        foreach ($results as $student){
            echo "</br>" . $student["student_id"] . " , " . $student["LAST"] . "</br>";

        }

        echo $sql;

    }
    public function findByStudentLastName($last_name){
        $sql = 'SELECT * FROM students WHERE LAST = :last_name';
        $this->adapter->prepare($sql);
        $place_holders = array(':last_name' => $last_name);
        $this->adapter->execute($place_holders);
        $results = $this->adapter->fetchAll();
        //print_r($results);
        foreach ($results as $student){
            echo "</br>" . $student["student_id"] . " , " . $student["LAST"] . "</br>";

        }
        echo $sql;

    }

}

The echo in the model here is for testing.

You can get away from implementing an interface and use a base class where the db connection and subsequent close are managed in the constructor. The query would be a parameter sent in to the constructor.

I think the MODEL in MVC is open to interpretation on how the plumbing is managed ( in terms of connections ), its just the naming convention that is important from table to controller depending on the framework.

I have done this a lot in php, but the only thing I have handy at the moment is python -> same premise though.

class db_query:

    oracle_instance = ''

    def __init__(self):
        print '-- new db instance --'

    def db_Query( self, host, port, sid, login, passwrd, queryString ):
        try:
            connstr = login + '/' + passwrd + '@' + host + ':' + port + '/' + sid
            connection    = cx_Oracle.connect( connstr )

        except cx_Oracle.DatabaseError as e:
            error, = e.args
            print(error.code)
            print(error.message)
            print(error.context)

        cursor = connection.cursor()
        cursor.arraysize = 200
        try:
            cursor.execute( queryString )
        except cx_Oracle.DatabaseError as e:
            error, = e.args    
            print(error.code)
            print(error.message)
            print(error.context)

        result = []

        for rows in cursor:
            result.append( rows )

        cursor.close()      
        connection.close()

        return result

Hope that gives you some ideas.