How do i return an error statement if the query is empty? - prepared-statement

Question

I would like echo something if the query is empty.
session_start();
include 'inc/db.php';
$student_id = $_POST['username'];
$password = $_POST['password'];
if($stmt = $conn->prepare("SELECT p.parent_id, ps.student_id, p.password
FROM parent p,
parentstudent ps
WHERE p.parent_id = ps.parent_id
AND student_id = ? limit 1")) {
$stmt->bind_param("s", $student_id);
$stmt->execute();
$stmt->bind_result($id, $student_id, $bindpassword);
while ($stmt->fetch()) {
if(password_verify($password, $bindpassword)){
$_SESSION['parent_id']= $id;
$_SESSION['student_id'] = $student_id;
header("location: parent.php");
}
else
echo "The student ID or password you have entered is inccorrect";
}
}
$stmt->close();

Answer 1

since you got only one row to retrieve from the database you could just replace the while with an if (i've deleted my previous response)
session_start();
include 'inc/db.php';
$student_id = $_POST['username'];
$password = $_POST['password'];
$stmt = $conn->prepare("SELECT p.parent_id, ps.student_id, p.password
FROM parent p,
parentstudent ps
WHERE p.parent_id = ps.parent_id
AND student_id = ? limit 1") ;
$stmt->bind_param("i", $student_id);
$stmt->bind_result($id, $student_id, $bindpassword);
$stmt->execute();
if($stmt->fetch()) {
if(password_verify($password, $bindpassword)){
$_SESSION['parent_id']= $id;
$_SESSION['student_id'] = $student_id;
header("location: parent.php");
}
else {
echo "The student ID or password you have entered is inccorrect";
}
}
else {
echo "nothing was fetch";
}
$stmt->close();
I've put two else, one if the password is incorrect, and one if there was no fetchs in the database