Error handler

Makes handling and debugging PHP errors suck less.

Contents

• Features
• Requirements
• Usage example
• Event system
  • Error handler events
  • Web error screen events
  • CLI error screen events
  • Event listener examples

Features

• normal / debug mode

• converts PHP errors (warnings, notices, etc.) into exceptions

• respects the global error_reporting setting

• handles uncaught exceptions and fatal errors (including parse and out-of-memory errors)

• CLI error screen writes errors to stderr

• web error screen renders errors for web browsers

  • normal mode shows a generic error message:

    
  • debug mode shows all available info:

    
    • file paths and line numbers
    • highlighted code previews
    • stack traces
    • argument lists
    • output buffer (can be shown as HTML too)
    • plaintext trace (for copy-paste)

• event system that can be utilised to:

  • implement logging
  • suppress or force errors conditionally
  • change or add content to the error screens

Requirements

• PHP 7.1+

Usage example

<?php

use Kuria\Error\ErrorHandler;

$debug = true; // true during development, false in production
error_reporting(E_ALL); // configure the error reporting

$errorHandler = new ErrorHandler();
$errorHandler->setDebug($debug);
$errorHandler->register();

// trigger an error to see the error handler in action
echo $invalidVariable;

Event system

Error handler events

Possible events emitted by the ErrorHandler class are listed in ErrorHandlerEvents:

ErrorHandlerEvents::ERROR

Emitted when a PHP errors occurs.

Arguments:

1. Kuria\Error\Exception\ErrorException $exception
   • you may use the suppress() or force() method to suppress or force the exception, respectivelly, regardless of the error_reporting PHP setting
2. bool $debug

ErrorHandlerEvents::EXCEPTION

Emitted when an uncaught exception or a fatal error is being handled.

Arguments:

1. Throwable $exception
2. bool $debug

Warning

Avoid performing memory-intensive tasks in listeners of this event if $exception is an instance of Kuria\Error\Exception\OutOfMemoryException.

ErrorHandlerEvents::FAILURE

Emitted when an uncaught exception or a fatal error could not be handled. This can happen when an exception event listener or the registered error screen throws an additional exception. Throwing another exception or causing a fatal error at this point will just kill the script.

Arguments:

1. Throwable $exception
2. bool $debug

Warning

Avoid performing memory-intensive tasks in listeners of this event if $exception is an instance of Kuria\Error\Exception\OutOfMemoryException.

Web error screen events

Possible events emitted by the WebErrorScreen class are listed in WebErrorScreenEvents:

WebErrorScreenEvents::RENDER

Emitted when rendering in normal mode.

Receives an array with the following keys:

• &title: used in <title>
• &heading: used in <h1>
• &text: content of the default paragraph
• &extras: custom HTML after the main section
• exception: the exception
• output_buffer: string|null

WebErrorScreenEvents::RENDER_DEBUG

Emitted when rendering in debug mode.

Receives an array with the following keys:

• &title: used in <title>
• &extras: custom HTML after the main section
• exception: the exception
• output_buffer: string|null

WebErrorScreenEvents::CSS

Emitted when CSS styles are being output.

Receives a single boolean value indicating debug mode.

WebErrorScreenEvents::JS

Emitted when JavaScript code is being output.

Receives a single boolean value indicating debug mode.

CLI error screen events

Possible events emitted by the CliErrorScreen class are listed in CliErrorScreenEvents:

CliErrorScreenEvents::RENDER

Emitted when rendering in normal mode.

Receives an array with the following keys:

• &title: first line of output
• &output: error message
• exception: the exception
• output_buffer: string|null

CliErrorScreenEvents::RENDER_DEBUG

Emitted when rendering in debug mode.

Receives an array with the following keys:ng keys:

• &title: first line of output
• &output: error message
• exception: the exception
• output_buffer: string|null

Event listener examples

Logging

Logging uncaught exceptions into a file:

<?php

use Kuria\Debug\Error;
use Kuria\Error\ErrorHandlerEvents;

$errorHandler->on(ErrorHandlerEvents::EXCEPTION, function (\Throwable $exception, bool $debug) {
    $logFilePath = sprintf('./errors_%s.log', $debug ? 'dev' : 'prod');

    $entry = sprintf(
        "[%s] %s: %s in file %s on line %d\n",
        date('Y-m-d H:i:s'),
        Error::getExceptionName($exception),
        $exception->getMessage(),
        $exception->getFile(),
        $exception->getLine()
    );

    file_put_contents($logFilePath, $entry, FILE_APPEND | LOCK_EX);
});

Disabling the "@" operator

This listener causes statements like echo @$invalidVariable; to throw an exception regardless of the "shut-up" operator.

<?php

use Kuria\Error\Exception\ErrorException;
use Kuria\Error\ErrorHandlerEvents;

$errorHandler->on(ErrorHandlerEvents::ERROR, function (ErrorException $exception, bool $debug) {
    $exception->force();
});

Altering the error screens

Note

Examples are for the WebErrorScreen.

Changing default labels in normal mode:

<?php

use Kuria\Error\Screen\WebErrorScreen;
use Kuria\Error\Screen\WebErrorScreenEvents;

$errorScreen = $errorHandler->getErrorScreen();

if (!$errorHandler->isDebugEnabled() && $errorScreen instanceof WebErrorScreen) {
    $errorScreen->on(WebErrorScreenEvents::RENDER, function ($event) {
        $event['heading'] = 'It is all your fault!';
        $event['text'] = 'You have broken everything and now I hate you.';
    });
}

Adding a customized section to the debug screen:

<?php

use Kuria\Error\Screen\WebErrorScreen;
use Kuria\Error\Screen\WebErrorScreenEvents;

$errorScreen = $errorHandler->getErrorScreen();

if ($errorHandler->isDebugEnabled() && $errorScreen instanceof WebErrorScreen) {
    // add custom CSS
    $errorScreen->on(WebErrorScreenEvents::CSS, function () {
        echo '#custom-group {color: #f60000;}';
    });

    // add custom HTML
    $errorScreen->on(WebErrorScreenEvents::RENDER_DEBUG, function (array $view) {
        $view['extras'] .= <<<HTML
<div id="custom-group" class="group">
 <div class="section">
     Example of a custom section
 </div>
</div>
HTML;
       });
   }