Advanced PHP · Lesson 10 of 10

Security Best Practices

Apply defense in depth to input, output, identity, and data access.

Lesson

Security is a set of layers: validate input, escape output for its context, parameterize SQL, use CSRF protection, hash passwords, enforce authorization, and keep dependencies updated. Store secrets outside source control and use HTTPS. Log security-relevant events without logging passwords, tokens, or sensitive personal data. Use least privilege and test failure paths, not only the successful path. Further guidance Make failure behavior explicit at system boundaries: validate decoded data, handle expected exceptions, and log diagnostics without exposing them to visitors. Keep dependencies locked and current, use a consistent namespace/autoloading scheme, and test error paths as well as successful responses. Practice task: Create a fresh example for Security Best Practices. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

PHP

$statement = $pdo->prepare('SELECT id FROM users WHERE email = :email');
$statement->execute(['email' => $email]);
$safeName = htmlspecialchars($name, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');

Expected output

A parameterized lookup and an HTML-escaped display value

Key points

Apply defense in depth to input, output, identity, and data access.
Handle expected errors explicitly without exposing diagnostics.
Keep dependency and runtime configuration reproducible.

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