I'd go one step further - you can't compare PHP to .NET directly.
PHP is directly comparable to Classic ASP, but for a truly apples-to-apples comparison you need to specify a PHP framework. Cake and Symfony are both popular, but the future of web app coding in PHP is the Zend Framework.
You should also learn design patterns, learn to use a source control system such as SVN or GIT, and learn your way around an IDE. Zend Studio for Eclipse is a good commercial option, or for free software Netbeans is good.