Has Many Through relation in laravel

The "has-many-through" relationship provides a convenient shortcut for accessing distant relations via an intermediate relation. For example, a Country model might have many Post models through an intermediate User model. In this example, you could easily gather all blog posts for a given country.

File name : index.php

countries
id - integer
name - string

users
id - integer
country_id - integer
name - string

posts
id - integer
user_id - integer
title - string

Though posts does not contain a country_id column, the hasManyThrough relation provides access to a country's posts via $country->posts. To perform this query, Eloquent inspects the country_id on the intermediate users table. After finding the matching user IDs, they are used to query the posts table.

File name : index.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Country extends Model
{
/**
* Get all of the posts for the country.
*/
public function posts()
{
return $this->hasManyThrough('App\Post', 'App\User');
}
}

The first argument passed to the hasManyThrough method is the name of the final model we wish to access, while the second argument is the name of the intermediate model.

If you would like to customize the keys of the relationship, you may pass them as the third and fourth arguments to the hasManyThrough method. The third argument is the name of the foreign key on the intermediate model. The fourth argument is the name of the foreign key on the final model. The fifth argument is the local key, while the sixth argument is the local key of the intermediate model:

File name : index.php

class Country extends Model
{
public function posts()
{
return $this->hasManyThrough(
'App\Post',
'App\User',
'country_id', // Foreign key on users table...
'user_id', // Foreign key on posts table...
'id', // Local key on countries table...
'id' // Local key on users table...
);
}
}

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