Advanced PHP · Lesson 3 of 10

Exceptions

Throw exceptions for failures and catch them at a meaningful boundary.

Lesson

Exceptions carry failure information up the call stack until a matching catch handles them. Catch only exceptions you can meaningfully recover from or translate; swallowing every Throwable hides defects. Use finally for cleanup that must happen whether an operation succeeds or fails. A custom exception can communicate a domain-specific failure to its caller. 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 Exceptions. 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

Exceptions

PHP

try {
    throw new DomainException('Order is already closed');
} catch (DomainException $exception) {
    echo 'Cannot update this order.';
}

Expected output

Cannot update this order.

Key points

Throw exceptions for failures and catch them at a meaningful boundary.
Handle expected errors explicitly without exposing diagnostics.
Keep dependency and runtime configuration reproducible.

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