In the framework jungle: CakePHP Basic Model

gistfile1.php

class User extends AppModel {

    public $validate = array(
        'email' => array(
            'isUnique' => array(
                'rule'     => 'isUnique',
                'message'  => 'This email is already used.'
            ),
            'email' => array(
                'rule'    => 'email',
                'message' => 'Enter a valid email.'
            )
        ),
        'password' => array(
            'rule'    => array('minLength', '8'),
            'message' => 'Minimum 8 characters long'
        ),
    );
    public $hasMany = array(
        'Post' => array(
                'className' => 'Post',
                'foreignKey' => 'user_id',
        )
    );
}

class Post extends AppModel {
    //TODO: check us:
    public $validate = array(
        'name' => array(
            rule'    => array('minLength', '3'),
        ),
        'content' => array(
            'rule'    => array('minLength', '3'),
            'message' => 'Minimum 3 characters long'
        ),
    );

     public $hasAndBelongsToMany = array(
        'Tag' => array(
            'className'              => 'Tag',
            'joinTable'              => 'post_tags',
            'foreignKey'             => 'post_id',
            'associationForeignKey'  => 'tag_id',
            'unique'                 => true,
        )
    );

    //or simply 
    //public $hasAndBelongsToMany = array('Tag');

    public $belongsTo = array(
        'User' => array(
            'className'    => 'User',
            'foreignKey'   => 'user_id'        
        )
    );
}

class Tag extends AppModel {

    public $hasAndBelongsToMany = array(
        'Post' => array(
            'className'              => 'Post',
            'joinTable'              => 'post_tags',
            'foreignKey'             => 'tag_id',
            'associationForeignKey'  => 'post_id',
            'unique'                 => true,
        )
    );
    
    //or simply 
    //public $hasAndBelongsToMany = array('Post');
}