$table->unsignedBigInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');// for laravel 7 or above.
$table->foreignId('user_id')->constrained();
/*-----------OR---------------*/
$table->foreignId('user_id')->constrained('users');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->foreign('column_name')->references('id')->on('table_name')->onDelete('cascade');$table->foreignId('post_id')
->constrained()
->onUpdate('cascade')
->onDelete('cascade');