PHP PDO (PHP Data Objects) is a versatile database access extension that allows developers to interact with various database systems using a consistent and secure interface. It offers a wide range of features for database operations. Below, I’ll cover some basic and advanced features of PHP PDO along with examples.

Basic Features:

1. Connection: To establish a connection to a database, use the PDO constructor. Example:

   $dsn = "mysql:host=localhost;dbname=database_name";
   $username = "username";
   $password = "password";

   try {
       $conn = new PDO($dsn, $username, $password);
   } catch (PDOException $e) {
       die("Connection failed: " . $e->getMessage());
   }

2. Query Execution: You can execute SQL queries using the query() method. Example:

   $sql = "SELECT * FROM users";
   $stmt = $conn->query($sql);

3. Fetching Data: Use the fetch() method to retrieve data. Example:

   while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
       echo "Username: " . $row['username'] . "<br>";
   }

4. Prepared Statements: PDO supports prepared statements for secure queries. Example:

   $sql = "SELECT username, email FROM users WHERE id = :id";
   $stmt = $conn->prepare($sql);
   $stmt->bindParam(':id', $id, PDO::PARAM_INT);
   $stmt->execute();
   $result = $stmt->fetch(PDO::FETCH_ASSOC);

Advanced Features:

1. Error Handling: PDO offers robust error handling through exceptions. Example:

   try {
       // Database operations
   } catch (PDOException $e) {
       echo "Error: " . $e->getMessage();
   }

2. Transactions: PDO supports transactions. You can use beginTransaction(), commit(), and rollBack() to handle transactions. Example:

   try {
       $conn->beginTransaction();
       // Perform database operations
       $conn->commit();
   } catch (PDOException $e) {
       $conn->rollBack();
       echo "Transaction failed: " . $e->getMessage();
   }

3. Named Placeholders: PDO allows the use of named placeholders in prepared statements. Example:

   $sql = "INSERT INTO table (column1, column2) VALUES (:value1, :value2)";
   $stmt = $conn->prepare($sql);
   $stmt->bindParam(':value1', $value1, PDO::PARAM_STR);
   $stmt->bindParam(':value2', $value2, PDO::PARAM_INT);

4. Multiple Statements: PDO can execute multiple SQL statements in a single call. Example:

   $sql = "INSERT INTO table1 VALUES ('value1'); INSERT INTO table2 VALUES ('value2')";
   $conn->exec($sql);

5. Stored Procedures: You can call stored procedures using PDO. Example:

   $sql = "CALL procedure_name(:param1, :param2)";
   $stmt = $conn->prepare($sql);
   $stmt->bindParam(':param1', $param1, PDO::PARAM_INT);
   $stmt->bindParam(':param2', $param2, PDO::PARAM_STR);
   $stmt->execute();

6. Database Independence: PDO allows you to switch between different database systems by changing the DSN, making it database-independent. Example:

   // Switching to SQLite
   $dsn = "sqlite:/path/to/database.db";
   $conn = new PDO($dsn);

7. Attribute Setting: You can set various attributes for your PDO connection, such as error handling and emulation mode. Example:

   $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
   $conn->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

This is a broad overview of some basic and advanced features of PHP PDO. In practice, you can combine these features to perform complex database operations securely and efficiently. PHP PDO is a powerful and flexible extension that can be used with various database systems, and it is a popular choice for working with databases in PHP applications.