with condition in laravel eloquent code example

Example 1: laravel where condition on relationship

App\Request::where('id',4)
    ->whereHas('quotes', function ($query) {
        $query->where('status','=','3');
    })
    ->with('quotes','sourceTable','destinationTable')
    ->get();

Example 2: laravel adding condition to relation

class Game extends Eloquent {
    // many more stuff here

    // relation without any constraints ...works fine 
    public function videos() {
        return $this->hasMany('Video');
    }

    // results in a "problem", se examples below
    public function available_videos() {
        return $this->videos()->where('available','=', 1)->get();
    }
}

Example 3: laravel where condition with if

$query = DB::table('user_ads')
            ->join('ads', 'users_ads.ad_id', '=', 'ads.id')
            ->orderBy($column, $method);

if ($input['search']) {
    $query->where('short_description', $input['search']);
}

if ($input['category']) {
    $query->where('category', $input['category']);
}

$query->join('users', 'users_ads.user_id', '=', 'users.id')
    ->select('ads.id', 'ads.img1', 'ads.short_description', 'ads.category', 'ads.product', 'ads.price', 'users.city')

$result= $query->get();

return $result;