关于使用ssh2_exec修改user密码的有关问题

$con = ssh2_connect( 'IP', '22' );
    if ( ssh2_auth_password( $con, 'root', 'root_pwd' ) ) {
            $stream = ssh2_exec( $con, "passwd test\n123456\n123456\n" ); //把用户名“test”的密码改成“123456”
            echo $stream;
    } else echo 'Cannot log in';