Retrieving Error Codes with errorCode()

The errorCode() method returns a standardized SQLSTATE identifier corresponding to the last operation performed on the database or statement object. The code consists of five alphanumeric characters (e.g., "42S02" for a missing table). The main advantage of using codes instead of text descriptions is that it simplifies automating logic for handling specific errors within your code.

EXAMPLE

<?php
class Database {
    private $server = "localhost";
    private $username = "root";
    private $password = "";
    private $db_name = "pdo_db";
    public $connection;

    public function __construct() {
        try {
            // Added charset=utf8mb4 for character support
            $dsn = "mysql:host=" . $this->server . ";dbname=" . $this->db_name . ";charset=utf8mb4";
            $this->connection = new PDO($dsn, $this->username, $this->password);
            // Disable exceptions so we can check the error code manually
            $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT);
        } catch(PDOException $e) {
            die("Connection failed: " . $e->getMessage());
        }
    }

    public function checkError() {
        // Intentionally incorrect SQL (table 'does_not_exist')
        $this->connection->query("SELECT * FROM does_not_exist");
        
        // Retrieve the SQLSTATE error code
        $code = $this->connection->errorCode();
        
        return $code;
    }
}

// PART 3: Usage
$db = new Database();
$error_code = $db->checkError();

if ($error_code !== "00000") {
    echo "An SQL error occurred! Code: " . $error_code;
} else {
    echo "Query was successful.";
}
?>

RESULT

The result will be displayed here...

Practical Application: We use the errorCode method when we want to trigger specific actions in the application based on the type of error (e.g., if the code indicates a "duplicate entry", we show a friendly warning to the user). Check the process at home by following these steps:

Start the Apache and MySQL modules in the XAMPP control panel.
Ensure via phpMyAdmin that the users table exists within the pdo_db database.
The method returns a five-character string; if there was no error, the code represents success (usually "00000").
Insert the example below into a PHP file and intentionally make a mistake in the SQL command to see the code output.