Question: `Fatal error: Uncaught RuntimeException: Request have return error: Method not found; Request: {"jsonrpc":"2.0","method":"getblockcount","params":null,"id":1}; in jsonRPCClient.php:166`
I don't know what to do. I started monero-wallet-rpc on the port and configured the example.php with port, localhost, username and password.
First I was running with no-rpc-auth and it gave me same error, then I deleted that argument and launched and told me unauthorized, then I edited the example.php and same error is up.
I also launched monerod in screen.

Answer: 
getblockcount is a daemon RPC, but you mention monero-wallet-rpc mostly. It is likely you are trying to call this RPC on the wallet, not on the daemon, and the wallet rightfully errors out.
Try params:{} maybe.

This one works for me:
`curl -X POST http://127.0.0.1:28081/json_rpc -d 
'{"jsonrpc":"2.0","id":"0","method":"getblockcount","params":{}}' -H 'Content-Type: application/json'`
`{
 "id": "0",
 "jsonrpc": "2.0",
 "result": {
 "count": 1097471,
 "status": "OK"
 }`