selecting from two tables on mysql

Question

I am trying to insert values by selecting from two different tables last inserted values. This code should work but it gives me error in 'SELECT MAX(users.id). I am sure have spelled right. What else can be wrong?

$query1 = "INSERT INTO post(postid, userid,  readornot)
            SELECT MAX(post.postid), SELECT MAX(users.id), 
            :readornot FROM post, users  ";     
$select1 = $db->prepare($query1); ':readornot' => $readornot ));    

Answer 1

$query1 = "INSERT INTO post(postid, userid,  readornot)
           VALUES (
            (SELECT MAX(post.postid) FROM post) p, 
            (SELECT MAX(users.id) FROM users) u, 
            :readornot  
              )";     
$select1 = $db->prepare($query1); ':readornot' => $readornot ));

something like this, i think