Description:
------------
When the php.ini "mysql.trace_mode" option is set to true,
and you do a mysql_query with SQL_CALC_FOUND_ROWS,
the result of a SELECT FOUND_ROWS() will always be 1, no matter how many rows would have been returned (disregarding any LIMIT clause.)

changing mysql.trace_mode to false will make it return the correct number.

Reproduce code:
---------------
ini_set('mysql.trace_mode', true);

$result_id = mysql_query('SELECT SQL_CALC_FOUND_ROWS column FROM t LIMIT 5');

$rows = array();
while($row = mysql_fetch_assoc($result_id)) {
    $rows[] = $row;
}

$result_id = mysql_query('SELECT FOUND_ROWS()');

list($row_total) = mysql_fetch_row($result_id);

Expected result:
----------------
$row_total will be the number of rows returned if there were no LIMIT clause.

Actual result:
--------------
$row_total is 1, regardless of the actual found rows.