Prevent E_NOTICE, E_WARNING, E_DEPRECATED errors WSOD in Sage 10

ThemeServiceProvider.php

<?php

namespace App\Providers;

use Roots\Acorn\ServiceProvider;

class ThemeServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->booted(
            function($app) {
                set_error_handler(function ($level, $message, $file = '', $line = 0, $context = []) {
                    // Check if this error level is handled by error reporting
                    if (error_reporting() & $level) {
                        // Return false for any error levels that should
                        // be handled by the built in PHP error handler.
                        if ($level & (E_WARNING | E_NOTICE | E_DEPRECATED)) {

                            echo "<br />\n";
                            echo "<b>ERROR</b> [$level] $message<br />\n";
                            echo "  Fatal error on line $line in file $file";
                            echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";
                            echo "Aborting...<br />\n";

                            return false;
                        }

                        // Throw an exception to be handled by Laravel for all other errors.
                        throw new \ErrorException($message, 0, $level, $file, $line);
                    }
                });
            }
        );

    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {

    }
}

Wow!!! Great @mike-sheppard !! I was struggling a bit with the environment and echoing the message as I'm using this in a project that has WooCommerce and, in the checkout page, if I echo the error (the one that you have styled), the review order part, that refreshes with AJAX (order items and totals), stops working... just to let you know...

Maybe it has sth to do with echoing before rendering...

Anyway...

aha yeah I see, how about only outputting to admin_footer/footer and prevent display in ajax, ie. just log to the logfile?

Something like this..

// app/Providers/ThemeServiceProvider.php
<?php

namespace App\Providers;

use ErrorHelper;
use function Roots\view;
use Illuminate\Support\Facades\Log;
use Roots\Acorn\ServiceProvider;

class ThemeServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->booted(
            function ($app) {
                set_error_handler(function ($level, $message, $file = '', $line = 0, $context = []) {
                    // Check if this error level is handled by error reporting
                    if (error_reporting() & $level) {
                        // Return false for any error levels that should be handled by the built in PHP error handler.
                        if ($level & (E_WARNING | E_NOTICE | E_DEPRECATED)) {
                            $error_label = ErrorHelper::getErrorTypeByValue($level) ?? '';
                            $error_output = view('admin.error', [
                                'error_label' => $error_label,
                                'message'     => $message,
                                'file'        => $file,
                                'line'        => $line,
                            ]);

                            if (is_admin() && !wp_doing_ajax()) {
                                add_action('admin_footer', function () use ($error_output) {
                                    echo $error_output;
                                });
                            } elseif (!wp_doing_ajax()) {
                                add_action('footer', function () use ($error_output) {
                                    echo $error_output;
                                });
                            }

                            // Also add to logfile / slack
                            $logfile_message = "Error displayed: {$error_label} - {$message}\n File: {$file}\n Line: {$line}";
                            (WP_ENV === 'development') ? Log::info($logfile_message) : Log::channel('slack')->warning($logfile_message);

                            return false;
                        }

                        // Throw an exception to be handled by Laravel for all other errors.
                        throw new \ErrorException($message, 0, $level, $file, $line);
                    }
                });
            }
        );

    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }
}

// ErrorHelper.php
<?php
class ErrorHelper
{
    public static function getErrorTypeByValue($type)
    {
        $constants = get_defined_constants(true);

        foreach ($constants['Core'] as $key => $value) { // Each Core constant
            if (preg_match('/^E_/', $key)) { // Check error constants
                if ($type == $value) {
                    return $key;
                }

            }
        }
    }

}

views/admin/error.blade.php

<pre style='position: fixed; z-index: 9999999; bottom: 1rem; right: 1rem; background: #eee; padding: 1rem; border-radius: 5px; box-shadow: 0 0 5px rgb(0 0 0 / 10%); border-left: 5px solid #ff5722; line-height: 1.8; max-width: 80%; overflow: scroll;'>
  <div style="position: absolute; top: 0; right: 0; font-size: 2rem; cursor: pointer; padding: 5px; line-height: 1;" onclick="return this.parentNode.remove();">&times;</div>
  <strong>{{ $error_label }}</strong> {{ $message }}
  File: {{ $file }}
  Line: {{ $line }}
</pre>

In your ajax scenario, maybe return with one of these?

if (wp_doing_ajax()) {
    ...
    wp_send_json( $response:mixed, $status_code:integer|null, $options:integer )
    wp_send_json_error( $data:mixed|null, $status_code:integer|null, $options:integer )
    ...
}

Docs: wp_send_json
Docs: wp_send_json_error

Works like a charm Mike... even with Ajax requests without using wp_send_json or wp_send_json_error.

Thank you again ;D

🙏 🙌