<?php

class Category extends Validate {

    protected $table = 'categories';
    public $timestamps = true;

    public function forum()
    {
        return $this->belongsTo('Forum');
    }

    public function topic()
    {
        return $this->hasMany('Topic');
    }

}


<?php

class Topic extends Validate {

    protected $table = 'topics';
    public $timestamps = true;

    public function user()
    {
        return $this->belongsTo('User');
    }

    public function category()
    {
        return $this->belongsTo('Category');
    }

    public function post()
    {
        return $this->hasMany('Post');
    }

}


<?php

class Post extends Validate {

    protected $table = 'posts';
    public $timestamps = true;

    public function user()
    {
        return $this->belongsTo('User');
    }

    public function topic()
    {
        return $this->belongsTo('Topic');
    }

}