How do I use PDO to connect to a database?
Jun 24, 2025 am 12:50 AM
To connect to a database using PDO in PHP, provide the DSN, username, and password within a try-catch block to handle errors gracefully. 1) Set up the DSN with database type, host, and name. 2) Use PDO to create a connection and set error mode to exception for better debugging. 3) Run queries using query() for simple selects or prepare() and execute() with placeholders to prevent SQL injection. 4) Handle errors by enabling exceptions or checking execute() return values. 5) Retrieve the last inserted ID using lastInsertId(). Always ensure credentials are correct and use proper placeholders for secure data handling.
Connecting to a database using PDO (PHP Data Objects) is a clean and secure way to interact with databases in PHP. Unlike older methods like mysql_* functions, PDO supports multiple database drivers and offers prepared statements, which help prevent SQL injection.
Here’s how to do it properly:
Basic PDO Connection Setup
To connect to a database using PDO, you need to provide the DSN (Data Source Name), username, and password. The DSN includes the type of database, host, and database name.
try {
$dsn = 'mysql:host=localhost;dbname=your_database_name';
$username = 'your_username';
$password = 'your_password';
$pdo = new PDO($dsn, $username, $password);
// Optional: Set error mode to exception for better debugging
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}This code tries to connect to a MySQL database hosted locally. If something goes wrong (like wrong credentials or unreachable server), it catches the exception and displays an error message.
A few things to watch out for:
- Make sure your database name, host, username, and password are correct.
- If you're not using MySQL, change the DSN accordingly (e.g.,
pgsql,sqlite, etc.)
Using PDO to Run Queries
Once connected, you can start running queries. Here's a basic example of selecting data from a table:
$stmt = $pdo->query('SELECT id, name FROM users');
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
echo 'ID: ' . $row['id'] . ' - Name: ' . $row['name'] . '<br>';
}If you're inserting or updating data, especially with user input, always use prepared statements to avoid SQL injection:
$stmt = $pdo->prepare('INSERT INTO users (name, email) VALUES (?, ?)');
$stmt->execute(['John Doe', 'john@example.com']);Or with named placeholders:
$stmt = $pdo->prepare('INSERT INTO users (name, email) VALUES (:name, :email)');
$stmt->execute(['name' => 'Jane Doe', 'email' => 'jane@example.com']);Using prepared statements ensures that user input is safely handled.
Handling Errors and Debugging
PDO doesn't throw exceptions by default, so it's a good idea to enable PDO::ERRMODE_EXCEPTION as shown earlier. That way, any errors during query execution will trigger an exception, making them easier to catch and debug.
If you want to check if a query was successful without exceptions:
if ($stmt->execute()) {
echo 'Query succeeded!';
} else {
echo 'Query failed.';
}You can also fetch the last inserted ID after an insert:
$lastId = $pdo->lastInsertId(); echo 'Last inserted ID: ' . $lastId;
For more complex applications, consider wrapping your database logic in a class or function to avoid repeating connection code everywhere.
That's the core of using PDO to connect to a database. It’s straightforward once you get the structure right, but don’t skip on error handling — it’ll save you time down the road.
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