Answers for "how to use foreign in laravel"

foreign key in laravel migration

$table->unsignedBigInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

laravel foreign key

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

    $table->foreign('user_id')->references('id')->on('users');
});
OR
Schema::table('posts', function (Blueprint $table) {
    $table->foreignId('user_id')->constrained();
});