Laravel get Error: Call to undefined function table()!

I am new in laravel. whene I want to run seed by this command: php artisan db:seed, I get this error: [Symfony\Component\Debug\Exception\FatalThrowableError] Call to undefined function table()

my two seeder class:

1- GroupTableSeeder

    <?php

    use Illuminate\Database\Seeder;
    use Illuminate\Database\Eloquent\Model;

    class GroupTableSeeder extends Seeder
    {
        /**
         * Run the database seeds.
         *
         * @return void
         */
        public function run()
        {
          DB::statement('SET FOREIGN_KEY_CHECKS=0');
          DB::table('groups')->truncate();

          $groups = [
            ['id' => 1, 'name' => 'Family',    'created_at' => new DateTime,         'updated_at' => new DateTime ],
            ['id' => 2, 'name' => 'Friends',   'created_at' => new DateTime, 'updated_at' => new DateTime ],
            ['id' => 3, 'name' => 'Customers', 'created_at' => new DateTime, 'updated_at' => new DateTime ],
            ['id' => 4, 'name' => 'CoWorkers', 'created_at' => new DateTime, 'updated_at' => new DateTime ],
            ['id' => 5, 'name' => 'Teachers',  'created_at' => new DateTime, 'updated_at' => new DateTime ]
          ];

          DB:table('groups')->insert($groups);
        }
    }

2- ContactsTableSeeder

    <?php

    use Illuminate\Database\Seeder;
    use Illuminate\Database\Eloquent\Model;
    use Faker\Factory as Faker;

    class ContactsTableSeeder extends Seeder
    {
        /**
         * Run the database seeds.
         *
         * @return void
         */
        public function run() {

          DB::table( 'contacts' )->truncate();

          $faker = Faker::create();

          $contacts = [];

          foreach ( range( 1, 20 ) as $index ) {

            $contacts[] = [
              'name'       => $faker->name,
              'email'      => $faker->email,
              'phone'      => $faker->phoneNumber,
              'address'    => "{$faker->streetName} {$faker->postcode}                 {$faker->city}",
              'company'    => $faker->company,
              'created_at' => new DateTime,
              'updated_at' => new DateTime,
            ];
          }

          DB::table( 'contacts' )->insert( $contacts );
        }
    }

and also my DatabaseSeeder class:

    <?php

    use Illuminate\Database\Seeder;
    use Illuminate\Database\Eloquent\Model;

    class DatabaseSeeder extends Seeder
    {
        /**
         * Run the database seeds.
         *
         * @return void
         */
        public function run()
        {
            $this->call(GroupTableSeeder::class);
            $this->call(ContactsTableSeeder::class);
        }
    }

please help me solve it. thanks.