Welcome,
prepare("SELECT photo, name FROM teachers WHERE id = ?");
$stmt->bind_param("i", $teacher_id);
$stmt->execute();
$result = $stmt->get_result();
$teacher = $result->fetch_assoc();
$photo_name = trim($teacher['photo'] ?? '');
$photo = (!empty($photo_name) && file_exists("uploads/teachers/" . $photo_name))
? "uploads/teachers/" . $photo_name
: "uploads/teachers/default.png";
?>
; ?>)