Running Your First SELECT Query with PDO

Connect, execute a SELECT query and fetch its columns safely before rendering HTML.

The objective is to understand the behavior and operational limits, not only the method name.

What It Does

Connect, execute a SELECT query and fetch its columns safely before rendering HTML.

Prerequisites

Use a dedicated development environment and sample data. Where a snippet uses an injected connection, repository, request value or mailer, supply it from your own application setup.

Example 1: Basic Use

A focused working pattern for this topic. Names such as $pdo, $authContext and $repo represent dependencies provided by the application unless initialized in the snippet.

<?php
$pdo = new PDO(getenv('DB_DSN'), getenv('DB_USER'), getenv('DB_PASSWORD'));
$stmt = $pdo->query('SELECT id, name FROM products ORDER BY id LIMIT 10');
foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $row) {
    echo htmlspecialchars($row['name'], ENT_QUOTES, 'UTF-8') . PHP_EOL;
}

Example 2: A Second Scenario

A second use case that adds a different operation or data flow specific to this topic.

<?php
$stmt = $pdo->prepare('SELECT id, name FROM products WHERE id = ?');
$stmt->execute([12]); $row = $stmt->fetch(PDO::FETCH_ASSOC);
if ($row === false) echo 'Not found'; else echo htmlspecialchars($row['name'], ENT_QUOTES, 'UTF-8');

Example 3: Practical Checks

A practical validation, failure or deployment concern specific to this topic.

<?php
$stmt = $pdo->query('SELECT COUNT(*) FROM products');
echo 'Products in catalog: ' . (int) $stmt->fetchColumn();

Important Behavior and Edge Cases

Do not assume fetch always returns a row; it returns false when the result is empty.

For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Connect, execute a SELECT query and fetch its columns safely before rendering HTML.
• Do not assume fetch always returns a row; it returns false when the result is empty.
• Use this workflow as a focused starting point rather than a substitute for application-level tests.

Choose this API or pattern when its exact semantics match your task, and verify the result against the database driver and runtime used by your application.