PHP PDO Database Access Cheat Sheet

Covers connecting with PDO, writing prepared statements, handling transactions, and key fetch and error mode configuration options.

1 PageIntermediateApr 12, 2026

Connecting with PDO

Opening a database connection with safe defaults.

php

try {    $pdo = new PDO(        "mysql:host=localhost;dbname=myapp;charset=utf8mb4",        "dbuser",        "dbpass",        [            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,        ]    );} catch (PDOException $e) {    die("Connection failed: " . $e->getMessage());}

Prepared Statements

Safely binding parameters to queries.

php

// SELECT with named placeholders$stmt = $pdo->prepare("SELECT * FROM users WHERE email = :email");$stmt->execute(['email' => 'jane@example.com']);$user = $stmt->fetch();// INSERT with positional placeholders$stmt = $pdo->prepare("INSERT INTO posts (title, body) VALUES (?, ?)");$stmt->execute([$title, $body]);$newId = $pdo->lastInsertId();// Fetching multiple rows$stmt = $pdo->query("SELECT id, name FROM users");foreach ($stmt->fetchAll() as $row) {    echo $row['name'];}

Transactions

Grouping statements atomically with commit and rollback.

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try {    $pdo->beginTransaction();    $pdo->prepare("UPDATE accounts SET balance = balance - ? WHERE id = ?")        ->execute([100, 1]);    $pdo->prepare("UPDATE accounts SET balance = balance + ? WHERE id = ?")        ->execute([100, 2]);    $pdo->commit();} catch (PDOException $e) {    $pdo->rollBack();    throw $e;}

PDO Concepts

Fetch modes, error handling, and binding methods.

PDO::FETCH_ASSOC- Returns rows as associative arrays keyed by column name
PDO::FETCH_OBJ- Returns rows as stdClass objects with column names as properties
PDO::ERRMODE_EXCEPTION- Makes PDO throw a PDOException on errors instead of failing silently
bindParam vs bindValue- bindParam binds by reference and reads the value at execute time; bindValue binds the value immediately
lastInsertId()- Returns the auto-increment ID generated by the most recent INSERT
Prepared statements- Separate SQL structure from data, automatically preventing SQL injection when placeholders are used

Pro Tip

Always use prepared statements with bound parameters instead of string-interpolating values into SQL — it's the single most effective defense against SQL injection in PHP.

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