Whether you use ASP or PHP to build dynamic websites is largely a matter of preference, but there are some things to think about before you make your choice.
If you want a programming language that offers a lot of support, then ASP might be to your advantage. PHP, being open source, has a support community, but that community is made up of volunteers. Your support will largely come from posting in forums and Q&A sites.
ASP is a programming language developed by Microsoft. That makes it proprietary. But there is advantage to using ASP that PHP can’t match. If you go the step further and use ASP.NET, which is a Web application framework, then you’ll have access to WYSIWYG editors and other developer helps that make development easier and quicker.
ASP is also typically used on Windows servers whereas PHP is more typically used on Linux servers. However, PHP is open source, which makes it more flexible and therefore able to integrate more easily into a Windows environment. While you can integrate ASP.NET into a Linux environment, it’s not as easy as going the other way.
Which programming language you use for your development projects is your decision. I hope these points are helpful in aiding you to decide.