How can the code be improved to handle cases where the user or key does not exist in the database?

When the user or key does not exist in the database, the code can be improved by checking if the query returned any results before trying to access them. This can be done by using the `rowCount()` method to determine if there are any rows returned by the query. If no rows are found, an appropriate error message can be displayed to the user. 

// Check if the query returned any results
if($stmt->rowCount() > 0) {
    // Fetch the user's data
    $row = $stmt->fetch(PDO::FETCH_ASSOC);
    
    // Access the user's data
    $username = $row['username'];
    $email = $row['email'];
    
    // Display the user's information
    echo "Username: $username<br>";
    echo "Email: $email<br>";
} else {
    // Display an error message if user or key does not exist
    echo "User not found.";
}

Keywords

error handling isset database query try catch exception handling

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