Select within select for MYSQL

Select within select for MYSQL

I am trying to SELECT specific lines of data from a MYSQL database
The database is as follows
Count id Startstation stp
1 A1234 Nottingham o
2 A1234 Nottingham p
3 B2345 Nottingham p
4 C6789 Leeds o
I would like to select all the Nottingham stations but not repeat the same
id. Also an stp code of o takes priority over an stp of p.
So I am looking for an output as follows:
A1234 Nottingham o
B2345 Nottingham p
Here is the code I have been trying to use but I cannot get it to work
require('connect_db.php');
mysqli_select_db($mysql_link,"timetable");
$q="select * from (SELECT id,startstation, stp, ROW_NUMBER() OVER
(PARTITION BY id ORDER BY stp DESC) rnk FROM railtest WHERE
startstation="Nottingham") where rnk = 1";
$r=mysqli_query($mysql_link,$q);
if ($r)
{
while ($row=mysqli_fetch_array($r,MYSQLI_ASSOC))
{
echo $row['startstation'] . " " . $row['id']." ".$row['stp'];
echo "<br>";
}
}
else {echo '<p>'.mysqli_error($mysql_link).'</p>' ;}
mysqli_close($mysql_link);
I am getting a Parse error with my select statement
Hope some one can help
Thanks