Number of rows effected returns zero for same and invalid data in PHP

Users table

 Id    Name     Email 
 1     Mike     mike@gmail.com
 2     John     john@gmail.com

Running UPDATE query with php Mysqli

$sql = "UPDATE users SET email=? WHERE id=?";
$stmt= $conn->prepare($sql);
$stmt->bind_param("si", $name, $id);
$stmt->execute();
$rowsEffected = $stmt->affected_rows;

Scenario1:

UPDATE users SET email='mike@gmail.com' WHERE id=1"

The above scenario returns $rowsEffected as zero as the data is same as before.

Scenario 2:

UPDATE users SET email='tyson@gmail.com' WHERE id=1"

The above scenario returns $rowsEffected as one as the data is not same as before.

Scenario 2:

UPDATE users SET email='eric@gmail.com' WHERE id=100"

The above scenario returns $rowsEffected as zero as the Id does not exists.

Here in the above scenarios, how to determine whether the update has been successful or not. How to differentiate between scenarios 1 , 2 with 3. I meant how to can we test whether an invalid update request with Id happens.