Bitcoind could not locate RPC credentials but rpcuser and password are set I installed bitoind and synced it. But when i'm trying to connect from my php website i getting: 
Unable to connect to http://user:password@my.bitoind.server.ip:18332/. 
Also when i'm trying to see password through command

bitcoin-cli -stdinrpcpass getblockchaininfo 

it returns 

could not locate RPC credentials. No authentication cookie could be found, and RPC password is not set.  See -rpcpassword and -stdinrpcpass.  Configuration file: (/blockchain/.bitcoin/bitcoin.conf). 

My bitcoin.conf file is setted and works nice

rpcuser=USER
rpcpassword=PASS
testnet=0
daemon=1
rpcport=18332
rpcallowip=*
server=1
datadir=/blockchain/.bitcoin
txindex=1
I found I had to copy the contents of ~/.bitcoin/bitcoin.conf into /etc/bitcoin/bitcoin.conf because that's what's being used when bitcoind starts on boot up. I put my user and password in that file, rebooted, and bitcoin-cli worked again.

Also try adding

bitcoin-cli -stdinrpcpass getblockchaininfo -rpcuser user -rpcpassword password