Perhaps you could reword your question, as it is hard to discern what exactly you are asking for.
In the meantime, check out http://us2.php.net/date.
It has a lot of useful examples for comparing dates, such as this:
$tomorrow = mktime(0, 0, 0, date("m") , date("d")+1, date("Y"));
So, perhaps you can do something like this would help:
$yesterday = mktime(0, 0, 0, date("m"), date("d")-1, date("Y"));
$yesterday = date("Y-m-d", $yesterday);
"SELECT * FROM resolved WHERE closed > " . $yesterday