The mysqli_connect_error() function is identical to the corresponding mysqli_connect_errno() function in every way, except instead of returning an integer error code the mysqli_connect_error() function will return a string representation of the last error to occur for the last mysqli_connect() call. If no error has occured, this function will return an empty string.
mysqli_connect(), mysqli_connect_errno(), mysqli_errno(), mysqli_error() and mysqli_sqlstate().