ASP- Closed source(developed by Microsoft)
Both PHP and ASP are great languages for most projects that need the server power and capabilities available with them.
Both ASP and PHP have several tools and available options with their GUI options.PHP is capable of being installed quickly and easily with many tools server side which can include image manipulation, uploading, email systems and much more.
ASP is designed to require registration of components and modules to make each tool possible. ASP will usually require paying for each component upgrade as well.
PHP works fine on both environments. Linux/BSD server will run the PHP scripts faster than a Windows. Both ASP and PHP languages are popular but PHP is more popular because of its Open License solutions, which can be implemented, free of cost or can be downloaded easily.