mysqli error: Cannot pass parameter 2 by reference in

mysqli error:

$stmt = $mysqli->prepare("INSERT INTO regex_comment (product_id,user_ip, uname, uemail, comments, sessionid )
VALUES ( ?, ?, ?, ?, ? ,? )" );

$stmt->bind_param('ssssss', '1', $i , $n, $e, $m, $s );

Correct :
$p=1;
$stmt = $mysqli->prepare("INSERT INTO regex_comment (product_id,user_ip, uname, uemail, comments, sessionid )
VALUES ( ?, ?, ?, ?, ? ,? )" );

$stmt->bind_param('ssssss', $p, $i , $n, $e, $m, $s );