Lesson 36 • Advanced

Cron Jobs & Task Scheduling ⏰

Automate recurring tasks with cron expressions, build a PHP task scheduler, and manage background workers with Supervisor.

What You'll Learn in This Lesson

• Read and write cron expressions for any schedule
• Build a PHP task scheduler with error handling
• Set up Linux crontab for automated PHP scripts
• Manage long-running worker processes with Supervisor
• Monitor worker pools and handle graceful shutdowns

Note: PHP runs on a server. Our examples simulate PHP logic using JavaScript. To run real PHP, install PHP.

🎯 Real-World Analogy: Cron jobs are like setting an alarm clock for your server. Just as you set alarms to wake up, take medication, or attend meetings, cron tells your server to clean up files at 3 AM, send email digests at 8 AM, and back up the database at 2 AM — all without human intervention.

Cron Syntax & Task Scheduling

Cron uses a five-field expression to define schedules: minute, hour, day of month, month, and day of week. An asterisk (*) means "every," and */5 means "every 5." Combine these to create any schedule from "every minute" to "first Monday of January at 3:15 AM."

Try It: Cron & Task Scheduler

Parse cron expressions and build a task scheduler with error handling

Try it Yourself »

JavaScript

// Cron Jobs: Automating Recurring Tasks
console.log("=== Understanding Cron Syntax ===");
console.log();
console.log("  ┌───── minute (0-59)");
console.log("  │ ┌───── hour (0-23)");
console.log("  │ │ ┌───── day of month (1-31)");
console.log("  │ │ │ ┌───── month (1-12)");
console.log("  │ │ │ │ ┌───── day of week (0-7, 0=Sun)");
console.log("  │ │ │ │ │");
console.log("  * * * * *  command");
console.log();

// Cron expression parser
class CronParser {
  constructor(expression, description) 
...

Background Workers

For tasks that need to run continuously (not just on a schedule), use long-running PHP worker processes. Supervisor ensures workers restart automatically if they crash, and pcntl_signal() enables graceful shutdown when deploying new code.

Try It: Worker Processes

Manage a pool of 4 workers with Supervisor and monitor their status

Try it Yourself »

JavaScript

// Background Workers & Process Management
console.log("=== PHP Worker Process Pattern ===");
console.log();
console.log("  // worker.php — Long-running background process");
console.log("  #!/usr/bin/env php");
console.log("  <?php");
console.log("  declare(ticks=1);");
console.log("  pcntl_signal(SIGTERM, function() {");
console.log("      echo 'Shutting down gracefully...';");
console.log("      exit(0);");
console.log("  });");
console.log();
console.log("  while (true) {");
console.log("   
...

⚠️ Common Mistakes

⚠️

Overlapping executions — If a cron job takes 10 minutes but runs every 5, you'll have multiple instances. Use lock files: flock -n /tmp/backup.lock php backup.php

⚠️

No output logging — Always redirect output to a log file (>> /var/log/cron.log 2>&1). Without it, debugging failures is impossible.

💡

Pro Tip: Laravel's scheduler lets you define cron jobs in PHP code instead of crontab: $schedule->command('emails:send')->dailyAt('08:00')

📋 Quick Reference — Cron & Workers

Concept	Description
crontab -e	Edit cron schedule for current user
flock	Prevent overlapping cron executions
Supervisor	Process manager for long-running workers
pcntl_signal()	Handle Unix signals for graceful shutdown
2>&1	Redirect stderr to stdout for logging

🎉 Lesson Complete!

You can now automate PHP tasks! Next, learn to manage environment configuration and secrets securely.