Ensure that the Laravel queue listener is running with "php artisan queue:checkup" and restart it if necessary. You can run this automatically with a cron job: http://laravel.com/docs/scheduling

cron.sh

#!/bin/bash
#
# You can run this bash script with a cron job
# or just run the command below.
#
# I had to use php-cli for both the cron job and the
# call to queue:listen in "EnsureQueueListenerIsRunning.php"
# to avoid getting the exception:
# 'ErrorException' with message 'Invalid argument supplied for foreach()'
# in /path/to/vendor/symfony/console/Input/ArgvInput.php:283
#

// php -d register_argc_argv=On /path/to/artisan schedule:run >/dev/null 2>&1 // by @giorgioprovenzale
php-cli /path/to/artisan schedule:run >/dev/null 2>&1

EnsureQueueListenerIsRunning.php

<?php

namespace App\Console\Commands;

use Illuminate\Console\Command;

class EnsureQueueListenerIsRunning extends Command
{
    /**
     * The name and signature of the console command.
     *
     * @var string
     */
    protected $signature = 'queue:checkup';

    /**
     * The console command description.
     *
     * @var string
     */
    protected $description = 'Ensure that the queue listener is running.';

    /**
     * Create a new command instance.
     */
    public function __construct()
    {
        parent::__construct();
    }

    /**
     * Execute the console command.
     *
     * @return void
     */
    public function handle()
    {
        if ( ! $this->isQueueListenerRunning()) {
            $this->comment('Queue listener is being started.');
            $pid = $this->startQueueListener();
            $this->saveQueueListenerPID($pid);
        }

        $this->comment('Queue listener is running.');
    }

    /**
     * Check if the queue listener is running.
     *
     * @return bool
     */
    private function isQueueListenerRunning()
    {
        if ( ! $pid = $this->getLastQueueListenerPID()) {
            return false;
        }

        $process = exec("ps -p $pid -opid=,cmd=");
        //$processIsQueueListener = str_contains($process, 'queue:listen'); // 5.1
        $processIsQueueListener = ! empty($process); // 5.6 - see comments

        return $processIsQueueListener;
    }

    /**
     * Get any existing queue listener PID.
     *
     * @return bool|string
     */
    private function getLastQueueListenerPID()
    {
        if ( ! file_exists(__DIR__ . '/queue.pid')) {
            return false;
        }

        return file_get_contents(__DIR__ . '/queue.pid');
    }

    /**
     * Save the queue listener PID to a file.
     *
     * @param $pid
     *
     * @return void
     */
    private function saveQueueListenerPID($pid)
    {
        file_put_contents(__DIR__ . '/queue.pid', $pid);
    }

    /**
     * Start the queue listener.
     *
     * @return int
     */
    private function startQueueListener()
    {
        //$command = 'php-cli ' . base_path() . '/artisan queue:listen --timeout=60 --sleep=5 --tries=3 > /dev/null & echo $!'; // 5.1
        //$command = 'php -d register_argc_argv=On ' . base_path() . '/artisan queue:work --timeout=60 --sleep=5 --tries=3 > /dev/null & echo $!'; // another solution by @giorgioprovenzale - see comments
        $command = 'php-cli ' . base_path() . '/artisan queue:work --timeout=60 --sleep=5 --tries=3 > /dev/null & echo $!'; // 5.6 - see comments
        $pid = exec($command);

        return $pid;
    }
}

Kernel.php

<?php

namespace App\Console;

use App\Console\Commands\EnsureQueueListenerIsRunning;
use Illuminate\Console\Scheduling\Schedule;
use Illuminate\Foundation\Console\Kernel as ConsoleKernel;

class Kernel extends ConsoleKernel
{
    /**
     * The Artisan commands provided by your application.
     *
     * @var array
     */
    protected $commands = [
        EnsureQueueListenerIsRunning::class
    ];

    /**
     * Define the application's command schedule.
     *
     * @param  \Illuminate\Console\Scheduling\Schedule $schedule
     *
     * @return void
     */
    protected function schedule(Schedule $schedule)
    {
        $schedule->command('queue:checkup')->everyFiveMinutes();
    }
}

I found a solution to use php without errors:
instead to use php-cli use php -d register_argc_argv=On

• giorgioprovenzale, on 14 Jul, added as a commented option in the gists