The bounding box query for SQL is(Using PDO)

    $sql ="SELCT bussid FROM tablename WHERE(latitude  BETWEEN ? AND ? )AND (longitude  BETWEEN ? AND ?)";
    $stmt = $dbh->prepare($sql);
    // Assign parameters
    $stmt->bindParam(1,$minLat);
    $stmt->bindParam(2,$maxLat);
    $stmt->bindParam(3,$minLng);
    $stmt->bindParam(4,$maxLng);

WHERE parameters come from top left  and bottom right of rectangle