Laravel logging configuration to send logs to PHP error log. (<= Laravel 5.5)

config - app.php

/*
|--------------------------------------------------------------------------
| Logging Configuration
|--------------------------------------------------------------------------
|
| Here you may configure the log settings for your application. Out of
| the box, Laravel uses the Monolog PHP logging library. This gives
| you a variety of powerful log handlers / formatters to utilize.
|
| Available Settings: "single", "daily", "syslog", "errorlog"
|
*/

'log' => env('APP_LOG', 'errorlog'),

'log_level' => env('APP_LOG_LEVEL', 'debug'),