PDO vs mysqli in PHP: Key Differences and When to Use Each

In PHP, PDO and mysqli are two ways to access MySQL databases. PDO supports multiple database types and offers a consistent API, while mysqli is specific to MySQL and provides both procedural and object-oriented interfaces.

Quick Comparison

Here is a quick side-by-side comparison of PDO and mysqli based on key factors.

Feature	PDO	mysqli
Database Support	Supports many databases (MySQL, SQLite, PostgreSQL, etc.)	Supports only MySQL
API Style	Object-oriented only	Supports procedural and object-oriented
Named Parameters	Yes, supports named placeholders	No, only positional placeholders
Prepared Statements	Supports prepared statements with emulation option	Supports native prepared statements
Error Handling	Uses exceptions by default	Uses error codes and warnings
Flexibility	More flexible for switching databases	Tied to MySQL features

Key Differences

PDO is a database access layer that works with many database types, making it easier to switch databases without rewriting code. It uses an object-oriented interface and supports named parameters in prepared statements, which can make queries easier to read and maintain.

mysqli is designed specifically for MySQL and offers both procedural and object-oriented styles. It supports native prepared statements and some MySQL-specific features like multiple statements and asynchronous queries. However, it only supports positional placeholders, which can be less clear in complex queries.

In terms of error handling, PDO throws exceptions by default, which helps catch errors cleanly, while mysqli requires checking error codes or warnings manually. Overall, PDO is more flexible and portable, while mysqli can offer more MySQL-specific features and options.

Code Comparison

Here is how you connect to a MySQL database and fetch data using PDO:

php

<?php
try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'pass');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

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

    echo 'User: ' . $user['name'];
} catch (PDOException $e) {
    echo 'Error: ' . $e->getMessage();
}

Output

User: Alice

mysqli Equivalent

Here is the equivalent code using mysqli in object-oriented style:

php

<?php
$mysqli = new mysqli('localhost', 'user', 'pass', 'testdb');

if ($mysqli->connect_error) {
    die('Connect Error: ' . $mysqli->connect_error);
}

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

echo 'User: ' . $user['name'];

$stmt->close();
$mysqli->close();

Output

User: Alice

When to Use Which

Choose PDO when you want database flexibility, cleaner error handling with exceptions, and support for named parameters. It is ideal if you might switch databases or want a consistent API across different systems.

Choose mysqli when you need MySQL-specific features, want to use procedural code, or require advanced MySQL options like asynchronous queries. It can be better if you are certain your project will only use MySQL and want direct access to its features.

Key Takeaways

PDO supports multiple databases and uses exceptions for error handling.

mysqli is MySQL-specific and supports both procedural and object-oriented styles.

PDO allows named parameters in prepared statements; mysqli uses only positional placeholders.

Use PDO for portability and cleaner code; use mysqli for MySQL-specific features.

Both support prepared statements to protect against SQL injection.