Description:
------------
mysqli_begin_transaction with MYSQLI_TRANS_START_READ_WRITE consistently returns FALSE even if there is no error reported with mysqli_error

PHP 7.0.13-0ubuntu0.16.04.1 (cli) ( NTS )

mysql  Ver 15.1 Distrib 10.1.21-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2

Was working on January 4, 2017.

database is InnoDB

Test script:
---------------
example:

$bd=mysqli_connect(NHOST,NUSER,NPASS,NNAME);
	if($bd==FALSE){
		echo mysqli_error();
	        return FALSE;
	}

if(mysqli_begin_transaction($bd,MYSQLI_TRANS_START_READ_WRITE)==FALSE){
		echo mysqli_error();
		mysqli_close($bd);
		return FALSE;
	}


Expected result:
----------------
Returning FALSE only when an error is found