- 01
What is the difference between == and === in PHP?
The == operator compares values after type juggling, while === requires both value and type to match. Strict comparison is safer when input types matter because it avoids surprising coercion.
- 02
How do interfaces, abstract classes, and traits differ?
Interfaces define a contract, abstract classes can combine a contract with shared state or behavior, and traits reuse method implementations across otherwise unrelated classes. The choice should reflect whether the design needs a public capability, a shared base abstraction, or implementation reuse.
- 03
What role does Composer play in a PHP project?
Composer resolves package dependencies, records versions in a lock file, and generates autoloading metadata. Production builds should install from the committed lock file so environments receive the same dependency graph.
- 04
How would you prevent SQL injection in PHP?
Question codephp$id = $_GET['id']; $result = $pdo->query("SELECT * FROM users WHERE id = $id");Use prepared statements with bound parameters and never concatenate untrusted input into SQL. Input validation, least-privilege database accounts, and safe ORM usage provide additional layers but do not replace parameterization.
Answer codephp$id = filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT); $stmt = $pdo->prepare('SELECT * FROM users WHERE id = :id'); $stmt->execute(['id' => $id]); $user = $stmt->fetch(); - 05
What should be considered when handling PHP sessions?
Session identifiers should use secure, HttpOnly, and appropriate SameSite cookies, and should be regenerated after authentication or privilege changes. Shared deployments also need a consistent session store and explicit expiration behavior.
- 06
How would you investigate a slow PHP endpoint?
Measure before changing code: inspect request traces, database queries, external calls, memory use, and cache behavior. Then address the dominant constraint and verify the improvement with the same workload.
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PHP Interview Questions and Answers
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