If you are trying to access a Windows Network Share you have to configure your WebServer with enough permissions for example:
$file = fopen("\\siscomx17\c\websapp.log",'r');
You will get an error telling you that the pathname doesnt exist this will be because Apache or IIS run as LocalSystem so you will have to enter to Services and configure Apache on "Open a session as" Create a new user that has enough permissions and also be sure that target share has the proper permissions.
Hope this save some hours of research to anyone.