What is the difference between mysqli and PDO in PHP?

Both mysqli and PDO are PHP extensions that provide a way to connect to and interact with databases. However, there are some key differences between mysqli and PDO:

1. API style: mysqli uses a procedural style API, while PDO uses an object-oriented style API. This means that mysqli functions are called using the traditional function call syntax, while PDO methods are called on objects.
2. Database support: mysqli is designed to work with MySQL databases only, while PDO can be used with a variety of databases including MySQL, PostgreSQL, SQLite, Oracle, and more.
3. Prepared statements: Both mysqli and PDO support prepared statements, which are an important tool for preventing SQL injection attacks. However, the syntax for prepared statements is slightly different between the two extensions.
4. Error handling: mysqli and PDO handle errors differently. mysqli provides both procedural and object-oriented error handling, while PDO provides only object-oriented error handling.
5. Performance: In terms of performance, mysqli can be faster than PDO in some cases because it is a lower-level extension that is specifically designed for MySQL. However, the performance difference is typically small and may not be noticeable in most applications.

Overall, the choice between mysqli and PDO will depend on your specific needs and preferences. If you are working with MySQL only and prefer a procedural style API, mysqli may be a good choice. If you need to work with multiple databases or prefer an object-oriented style API, PDO may be a better fit. Regardless of which extension you choose, it is important to use prepared statements and follow other best practices for writing secure and efficient database code in PHP.