laravel relationships

think of this relationship like a user table and user profile image, one user has one profile image this relationship is a very basic relation.

in user/image example a User model may be associated with one Photo. we can define this relationship by place a photo method on the User model.

Then we can access the photo method  and return its result:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * Get the Image record associated with the user.
     */
    public function photo()
    {
        return $this->hasOne('App\Photo');
    }
}

Note: you can change the foreign key and the references column

return $this->hasOne('App\Photo', 'foreign_key', 'local_key');

One to One Inverse Relationship

now you can define the inverse relationship between user and photo to access the user data by there photo  using the belongsTo method

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Photo extends Model
{
    /**
     * Get the user that owns the Photo .
     */
    public function user()
    {
        return $this->belongsTo('App\User');
    }
}

Define One to Many relationships

 One to Many relationships is the same relation between product and photo.

a single product can have on or more photo and the photo belong to a single product. 

now lets make our one to many relation between product and photo

in the product  Eloquent model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Product extends Model
{
    /**
     * Get the photo for the product
     */
    public function comments()
    {
        return $this->hasMany('App\Photo');
    }
}

Note: you can change the foreign key and the references column

return $this->hasMany('App\Photo', 'foreign_key', 'local_key');

One to Many Inverse Relationship

Now let's define the inverse of a hasMany the relationship that allows us to get the product from the photo.

you can use the belongsTo method on the photo Eloquent module

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Photo extends Model
{
    /**
     * Get the Ptoduct that owns the Photo.
     */
    public function product()
    {
        return $this->belongsTo('App\Product');
    }
}

Define Many to Many relationships

Many to Many relationships is considered one of the simplest relationships. Understanding it represents the participatory relationship between something like the relationship between a product and its category, where for each category there are more than one product and a single product may belong to more than one category.

In order to properly formulate it, we need 3 tables in the database one for a Product and one for the category and last one for the relation between product and category

product 
    id - integer
    name - string

category
    id - integer
    name - string

category_product 
    product_id - integer
    category_id - integer

Note. Remember to name the relation table "category_product" depending on that consists of the model names of the two main tables category, product, and that names are placed in alphabetical order and separated by a ( _ ).

Let's define the category method on our product model. to define the Many-to-many relationships we can use the belongsToMany method. For example

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Product extends Model
{
    /**
     * The category that belong to the product.
     */
    public function categorys()
    {
        return $this->belongsToMany('App\Category');
    }
}