PDO

PDO, or PHP Data Objects, is a consistent, object-oriented data access layer in PHP. It provides a lightweight, database-agnostic interface for performing common database operations through a uniform API, while delegating database-specific details to individual drivers. The goal is to allow applications to switch database systems with minimal code changes.

PDO relies on drivers that implement the extension for each database (for example, PDO_MYSQL, PDO_PGSQL, PDO_SQLITE). A connection is created with a DSN string, a username, and a password, plus optional driver options. Example DSN: mysql:host=localhost;dbname=testdb;charset=utf8mb4. Once connected, developers can use prepared statements, named or positional placeholders, and bound parameters.

Key features include prepared statements, which help prevent SQL injection; transactions with commit and rollback; a choice of fetch modes (e.g., FETCH_ASSOC, FETCH_NUM, FETCH_OBJ) and behavior for default results; and both named and positional parameter binding. PDO also supports persistent connections through options like ATTR_PERSISTENT and control over emulated prepared statements via ATTR_EMULATE_PREPARES.

Error handling is typically configured to throw exceptions (PDO::ERRMODE_EXCEPTION) to enable try-catch blocks. PDO does not implement a database driver itself; it provides a uniform API while the actual query execution is handled by the underlying database driver. While it supports many common features across drivers, some database-specific capabilities may require native SQL or driver functions.

Use of PDO is common in PHP applications that require database portability or a clean separation between SQL and application logic. It is not a database itself, but a consistent interface designed to simplify switching backends and to improve security and maintainability.