mysqli or PDO - what are the pros and cons?

mysqli and PDO are both PHP extensions used for interacting with databases.

mysqli (MySQL Improved) is specifically designed for MySQL databases and offers an object-oriented interface in addition to the traditional procedural interface. It also supports prepared statements, which can help prevent SQL injection attacks.

PDO (PHP Data Objects) is a more generic extension that provides a consistent interface for interacting with different types of databases (not just MySQL), using a variety of database drivers. It also supports prepared statements and offers an object-oriented interface.

Some of the pros of using mysqli include:

• It is specifically designed for MySQL databases and supports MySQL-specific features (e.g., multi-query, stored procedures).
• It has both procedural and object-oriented interfaces.
• Performance differences between mysqli and PDO are typically negligible in modern PHP.

Some of the cons of using mysqli include:

• It only works with MySQL databases and requires a separate extension for other types of databases.
• It does not provide a consistent interface for working with different types of databases.

Some of the pros of using PDO include:

• It provides a consistent interface for working with different types of databases using a variety of database drivers.
• It supports prepared statements and offers an object-oriented interface.
• It offers flexible error handling modes and multiple fetch styles.

Some of the cons of using PDO include:

• It does not provide a procedural interface.
• Performance differences are negligible, but PDO's abstraction layer can add slight overhead in highly optimized, database-specific scenarios.

Code Examples

Both extensions support prepared statements to prevent SQL injection. Below are minimal connection and query examples for each.

PDO

$pdo = new PDO('mysql:host=localhost;dbname=test', 'user', 'pass', [
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
]);

$stmt = $pdo->prepare('SELECT * FROM users WHERE id = :id');
$stmt->execute([':id' => 1]);
$user = $stmt->fetch();

mysqli

$mysqli = new mysqli('localhost', 'user', 'pass', 'test');
$mysqli->set_charset('utf8mb4');

$stmt = $mysqli->prepare('SELECT * FROM users WHERE id = ?');
$stmt->bind_param('i', $id);
$id = 1;
$stmt->execute();
$result = $stmt->get_result();
$user = $result->fetch_assoc();

Error Handling and Fetch Options

Error handling and data fetching are key decision factors when choosing between the two:

• PDO natively supports exception-based error handling via PDO::ERRMODE_EXCEPTION and provides multiple fetch modes (PDO::FETCH_ASSOC, PDO::FETCH_OBJ, PDO::FETCH_CLASS, etc.).
• mysqli defaults to warning-based error handling. To enable exception-based errors, you must call mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT). Fetching requires get_result() (enabled by default in modern PHP) or manual binding with bind_result().

In general, if you're only working with MySQL databases and performance is a critical concern, you might lean towards using mysqli, but if you need to work with multiple types of databases or want a consistent interface, PDO might be a better choice.