Question

Here is my model_users class (the “model” it extends from doesn’t have anything yet – still trying to work on getting this one ready and then abstracting out common functions for use with other models), Database::query just returns mysql_fetch_assoc() of the result:

class Model_User extends Model {    
    private static $_table = 'users';

    public function __construct($properties = array())
    {
        parent::__construct();
        foreach ($properties as $key => $value) {
            $this->{$key} = $value;
        }
    }

    public function exists()
    {
        return ($this->id) ? TRUE : FALSE;
    }

    public static function get_by_id($id = NULL)
    {
        if ($id)
        {
            $result = Database::query(
                sprintf('SELECT * FROM ' . self::$_table . ' WHERE id = %d', $id)
            );

            return new Model_User($result);
        }
        else
        {
            return new Model_User(array());
        }
    }

    public function save()
    {
        return TRUE;
    }
}

This allows me to do something like:

$u = Model_User::get_by_id(5);
        if ($u->exists())
        {
            echo $u->name;
            echo $u->id;
        }
        else
        {
            echo 'No user';
        }

I’m trying to learn how to use models without an orm or anything like it (I’ve used those before, but I want to learn how to do a simple version of them).

I’m wondering how to keep track of properties of a model in an abstract way, I’ve seen php’s reflection object and that might be what I need. I just want to be able to do things like:

$u = new Model_User();
$u->name = 'John';
$u->email = '[e-mail]';
$u->save();

or like

$u = Model_User::get_by_id(2);
$u->email = '[e-mail]';
$u->save();
// Different than the prior one since it would UPDATE, not INSERT

I’m not asking how to implement the entire save() method, but I need to know how to think about this in a way that can allow me to have an abstract model class that is easy to use. One of the barriers I need to get over is that there’s two types of properties, one type that is an actual property of the model (in this case ‘name’ or ’email’) and another type which has to do with other things such as ‘table name’ or maybe even some ‘has many’ relationships information.

Answer 1

One answer is: metadata.

You need to keep track of some data about your data.

If you want to have your db-columns exposed as plain-vanilla public properties on your model (and you don’t want to get into magic _get()/_set() stuff), you need to maintain a list, somewhere, of which properties need to be read/written from/to the db.

You could have something like;

<?php
class User extends Model {
    public $dbcols = array(
        'id',
        'name',
        'email'
    );
}

You save() method would then examine $this->dbcols to figure out what data it needs to worry about. In the above example, an update() method would do something like:

function update(){
    $updates = array();
    foreach($this->dbcols as $name){
        $updates[$name] = "'{$this->escape($this->$name))}'";
    }
    $sql = "UPDATE {$this->tableName} SET " . implode(',',$updates) . " WHERE id={$this->id}";
    ...
}

Of course, you could make $dbcols an associative array, and have different identifiers for your properties and column names, add validation or escaping rules, and eventually make things very complicated.