MySQL EXISTS return 1 or 0

How can I return the 1 or 0 as true and false for my select query? I've tried every combination of fetch_assoc, arrays, etc. It usually returns as null, which doesn't make sense.

$querydetails = "select exists (select * from customer_det where id = $uid)";
$resultdetails = mysql_query($querydetails) or die(mysql_error());
while ($row = mysql_fetch_assoc($resultdetails)) {
    $resultdetails1 = $row[0];
}

That's the latest version of my query. I guess it's not an array, but I'm not sure how to pull the value if there's no row to be named?

This is a post question to my previous thread: MySQL Update WHERE

SELECT IF(EXISTS(...),1,0) AS result

simple use COUNT and IF

SELECT IF(COUNT(*) = 0, 0, 1)
FROM table1
WHERE s = 2

• SQLFiddle Demo