Jquery datepicker con Ajax non funziona

<?php if(isset($_REQUEST['datepost']))
 {
 $date = date('m/d/Y',strtotime($_POST['date']));

 $res=mysql_query("SELECT * FROM  `wp_posts` WHERE DATE_FORMAT(post_date,  '%m/%d/%Y' ) =  $date AND post_type = 'post'  ORDER BY post_date DESC");
 $pageposts=mysql_fetch_array($res);

 exit();
 }  
?>

Fornisci il valore effettivo per la colonna post_date come DATE_FORMAT(post_date, '%m/%d/%Y' ) =$date