new PDO() Since: PHP 5（2004）

PDO is the standard interface for connecting to databases from PHP. It provides a unified API for working with multiple databases, including MySQL, PostgreSQL, and SQLite.

Syntax

// Connect to a database.
$pdo = new PDO($dsn, $username, $password, $options);

// Set a connection attribute.
$pdo->setAttribute($attribute, $value);

// Get a connection attribute.
$pdo->getAttribute($attribute);

Method List

Method	Description
new PDO($dsn, $user, $pass, $options)	Establishes a connection to the database. Throws a `PDOException` if the connection fails.
setAttribute($attribute, $value)	Sets an attribute on the PDO connection. You can configure error mode, fetch mode, character encoding, and more.
getAttribute($attribute)	Retrieves the current value of a connection attribute. Useful for checking the server version or driver name.

Common Connection Options

Constant	Description
PDO::ATTR_ERRMODE	Sets the error handling mode. Use `PDO::ERRMODE_EXCEPTION` to throw exceptions on errors.
PDO::ATTR_DEFAULT_FETCH_MODE	Sets the default fetch mode. Use `PDO::FETCH_ASSOC` to retrieve results as associative arrays.
PDO::ATTR_EMULATE_PREPARES	Set to `false` to use native prepared statements. Recommended for protection against SQL injection.
PDO::MYSQL_ATTR_INIT_COMMAND	Specifies an SQL command to run immediately after connecting to MySQL. Commonly used to set the character encoding.

Sample Code

<?php
// Basic connection to MySQL.
$dsn = 'mysql:host=localhost;dbname=myapp;charset=utf8mb4';
$username = 'db_user';
$password = 'db_password';

try {
	$pdo = new PDO($dsn, $username, $password);
	echo "Connected successfully"; // Output on successful connection.
} catch (PDOException $e) {
	echo "Connection failed: " . $e->getMessage();
}

// Recommended connection setup using an options array.
$options = [
	PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION, // Throw exceptions on errors.
	PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC, // Fetch results as associative arrays.
	PDO::ATTR_EMULATE_PREPARES => false, // Use native prepared statements.
];

$pdo = new PDO($dsn, $username, $password, $options);

// Connect to SQLite. No credentials needed since it is file-based.
$pdo_sqlite = new PDO('sqlite:/path/to/database.db');
$pdo_sqlite->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

// Connect to PostgreSQL.
$pdo_pg = new PDO('pgsql:host=localhost;dbname=myapp', 'user', 'password');

// Retrieve server information.
echo $pdo->getAttribute(PDO::ATTR_SERVER_VERSION); // Outputs something like '8.0.36'.
echo $pdo->getAttribute(PDO::ATTR_DRIVER_NAME); // Outputs 'mysql'.

// A practical example of managing the connection as a class.
class Database
{
	private static ?PDO $instance = null;

	public static function getConnection(): PDO
	{
		if (self::$instance === null) {
			$dsn = 'mysql:host=localhost;dbname=myapp;charset=utf8mb4';
			self::$instance = new PDO($dsn, 'user', 'password', [
				PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
				PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
				PDO::ATTR_EMULATE_PREPARES => false,
			]);
		}
		return self::$instance;
	}
}

$pdo = Database::getConnection();

Notes

PDO stands for PHP Data Objects. It is a class that provides an abstraction layer for database access. Always set PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION when connecting. The default silent mode ignores errors, making debugging very difficult.

You can set the character encoding by specifying charset=utf8mb4 in the DSN. utf8mb4 supports 4-byte UTF-8 characters including emoji, so it is preferred over utf8.

To execute SQL, use prepared statements via PDO::prepare(). To retrieve results, use fetch() / fetchAll(). For transaction control, use beginTransaction(). For handling connection errors, see try / catch.

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