Dynamically created web pages often cause problems with search engines. If your web pages are dynamically created, it’s likely that many search engines have difficulty to index them.Many search engines don’t like dynamically created pages because they might get in an infinite loop if they follow some dynamically created pages.
Google has an official statement about this in its webmaster guidelines:
“If you decide to use dynamic pages (i.e., the URL contains a “?” character), be aware that not every search engine spider crawls dynamic pages as well as static pages. It helps to keep the parameters short and the number of them few.