Add "ON DELETE CASCADE" to existing column in Laravel

Drop foreign key first. Thanks to Razor for this tip

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

In my case, i'll need to put the col name in an array else that will be an error.

Schema::table('transactions', function (Blueprint $table) {
    $table->dropForeign(['transactions_order_id_foreign']);
    $table->foreign('order_id')
        ->references('id')->on('orders')
        ->onDelete('cascade')
        ->change();
});

mysql 5.7 ver

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