Set Up Cron Jobs to Run PHP Scripts on DirectAdmin

A Cron Job is a scheduled task that runs scripts or commands automatically at set intervals. Common uses include sending daily emails, clearing caches overnight, running database backups, or triggering PHP scripts on a schedule. This step-by-step guide shows you how to configure Cron Jobs on DirectAdmin Hosting to run PHP scripts automatically.

What is a Cron Job?

Cron is a time-based job scheduler on Linux that runs tasks automatically at defined intervals. Scheduling uses a Cron Expression with five fields:

* * * * * command
│ │ │ │ └── Day of week (0-7, 0/7 = Sunday)
│ │ │ └──── Month (1-12)
│ │ └────── Day of month (1-31)
│ └──────── Hour (0-23)
└────────── Minute (0-59)

Common Cron Expression Examples

• 0 * * * * — Every hour
• 0 0 * * * — Every day at midnight
• 0 8 * * * — Every day at 08:00
• 0 0 * * 1 — Every Monday at midnight
• 0 0 1 * * — First day of every month at midnight
• */15 * * * * — Every 15 minutes
• */30 * * * * — Every 30 minutes

Cron Expression Reference for Common Schedules

Beyond the five-field syntax basics, here is a practical reference table of expressions used in real hosting scenarios, along with their typical use cases:

Setting Up a Cron Job in DirectAdmin

1. Log in to DirectAdmin
2. Go to Advanced Features → Cron Jobs
3. Fill in the Minute / Hour / Day / Month / Weekday fields
4. Enter the command to run
5. Click Add

Commands to Run PHP Scripts

Format 1 — Direct PHP Binary

/usr/local/php83/bin/php /home/username/public_html/cron/script.php

Format 2 — php-cli

/usr/bin/php /home/username/public_html/cron/script.php

Format 3 — wget (HTTP-based Cron)

wget -q -O /dev/null "https://yourdomain.com/cron/run.php" > /dev/null 2>&1

Format 4 — curl

curl -s "https://yourdomain.com/cron/run.php" > /dev/null 2>&1

Writing Cron-Friendly PHP Scripts

A script designed to run via cron should handle locking, error reporting, and environment differences from web requests. Here are the three most important patterns:

Prevent Overlapping Runs with a Lock File

If your cron fires every 5 minutes but the script takes 8 minutes to complete, a second instance will start before the first finishes, potentially causing data corruption or doubled work.

<?php
$lockFile = '/home/username/cron.lock';
if (file_exists($lockFile)) {
    // If lock is older than 10 minutes, it is stale — remove it
    if (time() - filemtime($lockFile) < 600) {
        exit("Script already running\n");
    }
}
file_put_contents($lockFile, getmypid());

try {
    // ... main work ...
} finally {
    unlink($lockFile); // always remove lock, even on error
}

Capture Errors and Send Alerts

Cron jobs are invisible — they run in the background and fail silently unless you build in error handling. Add this block at the top of every cron script:

<?php
set_error_handler(function($errno, $errstr, $errfile, $errline) {
    $msg = date('Y-m-d H:i:s')." ERROR [$errno] $errstr in $errfile:$errline\n";
    file_put_contents('/home/username/cron-error.log', $msg, FILE_APPEND);
    mail('[email protected]', 'Cron Error Alert', $msg);
});

register_shutdown_function(function() {
    $error = error_get_last();
    if ($error && in_array($error['type'], [E_ERROR, E_PARSE, E_CORE_ERROR])) {
        $msg = date('Y-m-d H:i:s')." FATAL: ".$error['message']."\n";
        file_put_contents('/home/username/cron-error.log', $msg, FILE_APPEND);
    }
});

Set the Correct Timezone

Cron runs in the server timezone, which is often UTC. If your schedule logic depends on local time, set the timezone explicitly at the top of your script:

<?php
date_default_timezone_set('Asia/Bangkok'); // UTC+7

// For database operations, also set MySQL timezone:
$pdo = new PDO('mysql:host=localhost;dbname=mydb', 'user', 'pass');
$pdo->exec("SET time_zone = '+07:00'");
echo date('Y-m-d H:i:s'); // Bangkok local time

Practical Cron Job Examples

Send daily report email at 08:00

0 8 * * * /usr/bin/php /home/username/public_html/send-email.php

Clear cache every night at midnight

0 0 * * * /usr/bin/php /home/username/public_html/clear-cache.php

Replace WP-Cron with a Real Cron Job

Add to wp-config.php: define('DISABLE_WP_CRON', true);

Then add this Cron Job:

*/5 * * * * /usr/bin/php /home/username/public_html/wp-cron.php > /dev/null 2>&1

Shared Hosting Limitations and How to Work Around Them

Shared hosting has constraints that differ significantly from a VPS. Understanding them upfront will save you from unexpected failures in production.

For scripts that run longer than 5 minutes, consume significant memory, or need to run more frequently than once per minute, consider upgrading to a VPS where there are no shared resource restrictions and you can use a full system crontab.

Verifying Your Cron Job Runs

Have your script write a log entry each time it executes so you can verify it later:

<?php
file_put_contents('/home/username/cron.log',
    date('Y-m-d H:i:s') . " - Script ran\n", FILE_APPEND);
// ... your script code