I have ordinal symfony project which includes 2 applications: public and admin parts. I need to move admin application files to project_path/web/admin. So if I call www.project.com/admin the admin project will be shown. How should I configure project to allow that ?
Moving an app to the document root would create a security hole since ALL your app files would be accessible to anyone if you don't secure them in any way. If you do not like the default symfony project setup which uses url rewriting for a single app only (the public one ususally) and want to have "clean urls" in other apps as well, you can create subdomains for them and set the "no_script_name" parameter in settings.yml to "on". For example, this way you could have urls like http://myap.domain.com/nice/url/here. In your case, the public app could be on domain.com and the admin app on admin.domain.com. Of course, you would have to configure your Apache vhosts accordingly - this is not something that symfony does for you out of the box.
Definitely do NOT move your files into web/admin
A solution to your problem will very likely be found in the project_path/apps/frontend/config/routing.yml
I had a similar problem before. I created a frontend module and called it "admin" then put links in it that linked to myproject/backend.php/table etc....
you can use the routing file to make www.project.com/admin work
to learn more: http://www.symfony-project.org/book/1_2/09-Links-and-the-Routing-System
remember to enable module_rewrite in you http.conf