PHP Shutdown Functions and Fatal Error Logging

Shutdown functions run when a PHP script terminates and can inspect the last error.

What It Does

Shutdown functions run when a PHP script terminates and can inspect the last error. The following examples distinguish a normal use case, a boundary case and a practical application.

Requirements and Compatibility

PHP 8.x and a local test environment. Apply input validation, correct error handling and the requirements of any optional libraries.

The code focuses on the core concept. Production implementation may also need routes, validation, persistence, authorization or deployment tooling.

Example 1: Basic Behavior

Start with the smallest meaningful working case.

<?php
set_error_handler(function (int $level, string $message): bool { echo 'Handled warning'; return true; });
trigger_error('Example warning', E_USER_WARNING);
restore_error_handler();

Example 2: Another Case

Examine the edge case and the observable result.

<?php
register_shutdown_function(function (): void { $last = error_get_last(); if ($last !== null) error_log('Shutdown code: ' . $last['type']); });
echo 'Shutdown handler registered';

Practical Example: Putting It to Use

Only treat selected error types as fatal and keep stack details out of responses.

<?php
register_shutdown_function(function (): void {
    $last = error_get_last();
    if ($last && in_array($last['type'], [E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR], true)) {
        error_log('Fatal category: ' . $last['type']);
    }
});
echo 'Shutdown monitor configured';

Important Behavior and Edge Cases

Not every termination guarantees cleanup, and error_get_last may report a nonfatal earlier error.

Comparison with Related Functions or Approaches

Common Beginner Mistakes

Key Takeaways

• Shutdown functions run when a PHP script terminates and can inspect the last error.
• Not every termination guarantees cleanup, and error_get_last may report a nonfatal earlier error.
• Use set_exception_handler() for uncaught exceptions and central logging for runtime events.

Before adapting these examples, verify the return values, test the failure paths and confirm that your application meets its security and environment requirements.