Advanced Error Handling 🚨

Build custom exception hierarchies, global error handlers, structured logging, and environment-aware error reporting.

What You'll Learn in This Lesson

• PHP's Throwable hierarchy: Error vs Exception
• Build custom exception classes with HTTP status codes
• Catch specific exception types for granular error handling
• Set up global exception and error handlers
• Structured logging with JSON for production monitoring

Note: PHP runs on a server. Our examples simulate PHP logic using JavaScript. To run real PHP, install PHP.

🎯 Real-World Analogy: Exception hierarchies are like a hospital triage system. Not every problem gets the same response. A ValidationException is a minor injury — fix the input and retry. A NotFoundException is a missing patient — search elsewhere. An AuthenticationException is someone without an ID badge — send them to reception. Each type gets routed to the right handler automatically.

Custom Exception Hierarchies

Instead of throwing generic Exception everywhere, create a hierarchy of custom exceptions. This lets you catch specific error types and respond appropriately — returning 404 for not-found errors, 422 for validation failures, and 500 for unexpected crashes.

Try It: Exception Hierarchy

Build and catch custom exceptions with status codes and specific error types

Try it Yourself »

JavaScript

// Custom Exception Hierarchies in PHP
console.log("=== Exception Hierarchy ===");
console.log();
console.log("PHP's built-in hierarchy:");
console.log("  Throwable");
console.log("  ├── Error (fatal — don't catch these normally)");
console.log("  │   ├── TypeError");
console.log("  │   └── DivisionByZeroError");
console.log("  └── Exception (your code should throw these)");
console.log("      ├── RuntimeException");
console.log("      ├── InvalidArgumentException");
console.log("      └── Logic
...

Global Handlers & Logging

A global exception handler catches anything that slips through your try-catch blocks. Combined with structured JSON logging, it ensures no error goes unnoticed and your production logs are machine-parseable for monitoring tools like ELK Stack, Datadog, or Sentry.

Try It: Global Handler & Logging

Set up global handlers, configure error reporting, and build structured loggers

Try it Yourself »

JavaScript

// Global Error Handler & Logging
console.log("=== Global Exception Handler ===");
console.log();
console.log("PHP lets you set a global handler for uncaught exceptions:");
console.log();
console.log("  set_exception_handler(function(Throwable $e) {");
console.log("      // Log the error (never show details to users!)");
console.log("      error_log($e->getMessage() . ' in ' . $e->getFile() . ':' . $e->getLine());");
console.log("      ");
console.log("      // Show user-friendly error page");
c
...

⚠️ Common Mistakes

⚠️

Catching Exception too broadly — catch (Exception $e) swallows everything. Catch specific types first, then fall back to a generic handler.

⚠️

Showing stack traces to users — never display $e->getTraceAsString() in production. Log it, but show users a friendly message.

⚠️

Empty catch blocks — catch (Exception $e) {} silently swallows errors. At minimum, log the exception.

💡

Pro Tip: Use PHP 8's match expression in your global handler to map exception types to HTTP responses cleanly.

📋 Quick Reference — Error Handling

Concept	Purpose
set_exception_handler()	Catch uncaught exceptions globally
set_error_handler()	Convert PHP errors to exceptions
error_reporting(E_ALL)	Report all errors (dev mode)
error_log()	Write to PHP error log file
Custom exceptions	Type-specific error handling with status codes
try / catch / finally	Handle errors with guaranteed cleanup

🎉 Lesson Complete!

You can now handle errors like a pro! Next, learn to consume REST APIs with cURL, Streams, and Guzzle.