create foreign key laravel migration

use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

Schema::table('posts', function (Blueprint $table) {
    $table->unsignedBigInteger('user_id');

    $table->foreign('user_id')->references('id')->on('users');
});

$table->foreignId('user_id')
      ->constrained("users") <- // You don't need to specify table if it matched laravel naming conventions.
      ->onUpdate('cascade')
      ->onDelete('cascade');