the question is WAY unclear, but I suspect you want something like
foreach ($arr as $key => $item) $arr[$key] = mysql_real_escape_string($item);
$in = "'".implode("','",$arr);
$sql = "SELECT id, pos, FROM $db WHERE dtime>='$now' AND jsub IN ($in)";
But man, I hate guessing.
Why don't you get yourself a static query, without any PHP code?
To see, if it ever works?
If not - ask on SO for the proper query. SQL query, not PHP code.
If yes - write a PHP code that produces the exact query.
Compare to the example one.
If failed - ask on SO for the PHP code, providing an example of the resulting query and an array.
Is it too hard rules to follow?