Your best bet is to download the Solr source and check the existing implementations Of RequestHandlers. There are some that are quiet simplistic and can give you a good grasp of the API and a starting point.PingRequestHandler comes first to mind, if your goal is to do something very simple. For more complex scenarios look for the ones that make use of components and take a look in solr config for their initialization parameters.

Best of luck!  

Custom Request Handlers/Components with Solr-4.x
That's really strange :So after i upload a folder with php files on another service,and try to execute them from a browser,i get 500 error.If i open a file in a text editor,save it with different name like file1.php,then erase the original,and rename the file1.php to the previous name,it works.
