7. Error Handling — Exceptions, Types, and Failure Modes

Error handling is where PHP reveals its maturity.
Modern PHP expects:

• typed arguments
  rejecting invalid input early
• typed returns
  guaranteeing what comes back
• predictable exceptions
  failures that are explicit, not hidden
• explicit failure modes
  no silent “false” or “null” surprises

AI often mixes old and new patterns, or generates code that hides errors instead of surfacing them.
This page gives us the mental model to recognize what “good” PHP error handling looks like.

Older PHP code often relied on:

• silent failures
  functions returning false without explanation
• false returns
  mixing success and failure in the same type
• warnings instead of exceptions
  errors that don’t stop execution
• error suppression (@)
  hiding problems instead of fixing them

Modern PHP is the opposite:

• strict types
  invalid input becomes an error, not a guess
• exceptions
  failures stop execution and bubble up
• explicit failure handling
  clear, predictable control flow

If AI generates code using old patterns, our mental model will flag it immediately.

PHP 7+ introduced real type safety:

function load(int $id): User { ... }

Types help you:

• catch mistakes early
  before the logic even runs
• document intent
  making the contract visible
• prevent invalid states
  the core of modern architecture
• simplify error handling
  fewer branches, fewer surprises

AI sometimes omits types or mixes nullable and non‑nullable types incorrectly.
Our understanding helps us correct that.

Instead of returning false or null, modern PHP throws exceptions:

throw new InvalidArgumentException("ID must be positive.");

And exceptions:

• stop execution
  preventing corrupted state
• bubble up the call stack
  letting higher layers decide what to do
• allow centralized handling
  one place to log, respond, or recover
• make failure explicit
  no ambiguity, no hidden branches

This is one of the clearest signs of modern PHP.

Good PHP code uses domain‑specific exceptions:

class UserNotFound extends RuntimeException {}

And this allows for:

• precise error handling
  catching only what we intend
• clearer debugging
  the exception name tells the story
• better architecture
  errors become part of the domain language

AI often uses Exception everywhere.
Our mental model helps us refine that.

The @ operator hides problems:

$result = @file_get_contents($path);

This is almost always a mistake.
Modern PHP expects you to handle errors, not hide them.

Frameworks and modern apps often have:

• a global exception handler
  one place to catch everything
• a logging layer
  consistent visibility into failures
• a consistent error response
  predictable behavior for clients

This keeps the codebase clean, stable, and easy to reason about.

Modern PHP error handling is:

• typed. explicit, exception‑driven, predictable, centralized

Once you internalize this, you can instantly see when AI‑generated code is living in the wrong era.

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