Seagull is described as 'object oriented framework written in PHP that focuses on best practices, clean code and reusable components' and is an app in the Development category. There are more than 25 alternatives to Seagull for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and Self-Hosted solutions. The best alternative is Django, which is both free and Open Source. Other great apps like Seagull are Laravel (Free, Open Source), Ruby on Rails (Free, Open Source), Symfony (Free, Open Source) and CodeIgniter (Free, Open Source).
Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design. Built by experienced developers, it takes care of much of the hassle of Web development, so you can focus on writing your app without needing to reinvent the wheel.
Nette Framework is a popular tool for PHP web development. It is designed to be the most usable as possible and is definitely one of the safest one. It speaks your language and helps you to easily build better websites.