RS232 to ethernet over LAN
If you want to extend Rs232, you can get "extenders over LAN" or there are converters available.


  Can I connect an rs232 ethernet converter to a switch and expect to
  receive a data on a php server listening to the of IP conversor?


IF the RS232 converter can be 'seen' (best by using a static IP, and having the subnets set up correctly) by the PHP server and the driver can be installed then yes, the data could be received like a normal COM port. RS232 over LAN is a bit different because of the delays, make sure you have good solid link that isn't dropping packets. Also, if your application requires hardware flow control then the link may not work exactly like a normal COM port.