You can use print() to send it as in the following:
int n_decimals = 3;
float PHValue = Value/10;
float DOValue= 12.22;
gprsSerial.print("AT+HTTPPARA=\"URL\",\"http://itempurl.com/smartpond/AddTemprature?WaterTemperature=");
gprsSerial.print(celsius, n_decimals);
gprsSerial.print("&PHValue=");
gprsSerial.print(PHValue, n_decimals);
gprsSerial.print("&DOValue=");
gprsSerial.print(DOValue, n_decimals);
gprsSerial.println("¤tTime=06-30-2016\"");
With n_decimals the number of decimal places that you want to be printed.
Or you can also use snprintf to generate your AT command:
char command[256];
float PHValue = Value/10;
float DOValue= 12.22;
snprintf(command, sizeof(command), "AT+HTTPPARA=\"URL\",\""
"http://itempurl.com/smartpond/AddTemprature?"
"WaterTemperature=%f&PHValue=%f&DOValue=%f"
"¤tTime=06-30-2016\"", celsius, PHValue, DOValue);
gprsSerial.println(command);