This guide demonstrates how to create PHP cron jobs on Linux server.

Table of Contents

What are PHP Cron Jobs?

Cron is the standard Linux scheduler used to run scripts automatically at defined intervals. PHP cron jobs are commonly used for automation tasks such as backups, billing runs, log cleanup, monitoring scripts, email campaigns, and application maintenance.

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This guide explains how to create, configure, and customize PHP cron jobs using command-line flags and parameters.

How to Create PHP Cron Jobs on Linux Server

To create PHP cron jobs on Linux server, follow the steps below:

Understanding Cron

Cron is a background daemon that executes commands based on a defined schedule stored in a crontab file.

A cron schedule has five time fields followed by the command to execute.

* * * * * command_to_run
│ │ │ │ │
│ │ │ │ └── Day of week (0–7) (Sun = 0 or 7)
│ │ │ └──── Month (1–12)
│ │ └────── Day of month (1–31)
│ └──────── Hour (0–23)
└────────── Minute (0–59)

Example:

0 2 * * * /usr/bin/php /scripts/backup.php

This runs backup.php every day at 2:00 AM.

Verify PHP CLI is Installed

Cron jobs should use the PHP CLI binary, not the web version.

Check the PHP CLI path:
```
which php
```
Typical results:
```
/usr/bin/php
```
Check version:
```
php -v
```
Example output:
```
PHP 8.2.10 (cli)
```
Create a Basic PHP Cron Script

Example script:
```
nano /scripts/test-cron.php
```
Example code:
```
 
```
Test it manually:
```
php /scripts/test-cron.php
```
Check output:
```
cat /tmp/cron_test.log
```
Editing the Crontab

Open the crontab editor:
```
crontab -e
```
Add a job:
```
*/5 * * * * /usr/bin/php /scripts/test-cron.php
```
This runs every 5 minutes.

Save and exit.

Verify cron jobs:
```
crontab -l
```
Using Full Paths (Very Important)

Cron runs with a minimal environment, so always use absolute paths.

Incorrect:
```
php test-cron.php
```
Correct:
```
/usr/bin/php /scripts/test-cron.php
```

Redirecting Output and Errors

Cron jobs generate output which may be emailed or logged.

Redirect output:

*/5 * * * * /usr/bin/php /scripts/test.php >> /var/log/php-cron.log

Redirect errors:

*/5 * * * * /usr/bin/php /scripts/test.php >> /var/log/php-cron.log 2>&1

Explanation:

>> append output
2>&1 send errors to same log

PHP CLI Flags for Cron Jobs

PHP CLI supports flags that customize execution.

Common flags include:

Flag	Purpose
`-c`	Specify custom php.ini
`-d`	Override configuration values
`-q`	Suppress HTTP headers
`-f`	Execute PHP script file
`-r`	Run PHP code directly
`-m`	Show loaded modules
`-n`	Ignore php.ini

Using the `-c` Flag (Custom php.ini)

The -c option specifies a custom configuration file.

Example:

/usr/bin/php -c /opt/custom-php.ini /scripts/worker.php

Use case:

Different memory limits for cron tasks.

Example custom config:

memory_limit = 1024M
max_execution_time = 0

Cron entry:

*/10 * * * * /usr/bin/php -c /opt/php-cron.ini /scripts/heavy-task.php

Using the `-d` Flag (Override Settings)

The -d flag temporarily overrides PHP settings.

Example:

php -d memory_limit=512M script.php

Cron example:

0 * * * * /usr/bin/php -d memory_limit=1024M /scripts/report.php

Multiple overrides:

php -d memory_limit=512M -d max_execution_time=0 script.php

Cron example:

0 1 * * * /usr/bin/php -d memory_limit=1G -d max_execution_time=0 /scripts/import.php

Using the -q Flag

The -q option suppresses HTTP headers.

Useful for older PHP scripts designed for CGI.

Example:
```
php -q script.php
```
Cron example:
```
*/15 * * * * /usr/bin/php -q /scripts/legacy-script.php
```

Using the `-f` Flag

The -f flag explicitly specifies a script file.

Example:

php -f /scripts/job.php

Cron example:

*/10 * * * * /usr/bin/php -f /scripts/cache-cleaner.php

Passing Arguments to PHP Scripts

PHP scripts can accept parameters.

Example script:
```
nano /scripts/backup.php
```
Example code:
```
 
```
Run manually:
```
php backup.php full
```
Cron example:
```
0 3 * * * /usr/bin/php /scripts/backup.php full
```

Combining Flags and Arguments

Example advanced cron job:

*/30 * * * * /usr/bin/php -d memory_limit=512M -d max_execution_time=0 /scripts/process-queue.php --limit=100

Explanation:

-d memory_limit=512M
-d max_execution_time=0
--limit=100 passed to script

Running PHP Inline with `-r`

You can execute PHP code directly.

Example:

php -r 'echo date("Y-m-d H:i:s");'

Cron example:

*/10 * * * * /usr/bin/php -r 'file_put_contents("/tmp/time.log", date("c").PHP_EOL, FILE_APPEND);'

Running as a Specific User

Cron jobs should run under the correct user.

Edit the user’s crontab:
```
crontab -e
```
System-wide cron:
```
/etc/crontab
```
Example:
```
0 1 * * * www-data /usr/bin/php /var/www/scripts/cleanup.php
```
Locking Cron Jobs (Prevent Overlap)

Prevent jobs from running simultaneously.

Example using flock:
```
*/5 * * * * flock -n /tmp/job.lock /usr/bin/php /scripts/job.php
```
Monitoring Cron Jobs

Check cron logs:
```
grep CRON /var/log/syslog
```
On RHEL / AlmaLinux:
```
grep CRON /var/log/cron
```

Example Production Cron Jobs

Queue Worker

* * * * * /usr/bin/php /var/www/app/artisan queue:work

Database Cleanup

0 4 * * * /usr/bin/php -d memory_limit=512M /scripts/db-clean.php

Cache Purge

*/30 * * * * /usr/bin/php /scripts/cache-purge.php >> /var/log/cache.log 2>&1

Backup Job

0 3 * * * /usr/bin/php -d memory_limit=2G /scripts/backup.php full >> /var/log/backup.log 2>&1

Security Best Practices
- Use CLI PHP
  
  Always use:
```
/usr/bin/php
```
  not:
```
/usr/local/bin/php-cgi
```
- Restrict Permissions
```
chmod 700 /scripts
```
- Avoid Running as Root
  
  Use a dedicated user:
```
www-data
deploy
automation
```
- Log Everything
```
>> /var/log/script.log 2>&1
```

Example Enterprise PHP Cron Stack

Example automation environment:

/opt/cron/
 ├── workers
 │   ├── queue.php
 │   └── billing.php
 ├── logs
 │   └── cron.log
 └── locks

Example cron entries:

*/1 * * * * flock -n /opt/cron/locks/queue.lock /usr/bin/php /opt/cron/workers/queue.php >> /opt/cron/logs/cron.log 2>&1

0 * * * * /usr/bin/php -d memory_limit=512M /opt/cron/workers/billing.php >> /opt/cron/logs/cron.log 2>&1

Testing Cron Jobs Safely

Test with:

run-parts --test /etc/cron.hourly

Or run manually:

sudo -u www-data /usr/bin/php /scripts/test.php

Troubleshooting

Cron not running

Check service:

systemctl status crond

Start if needed:

systemctl enable crond
systemctl start crond

PATH problems

Add PATH in crontab:

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Permission errors

Check user permissions:
```
ls -l script.php
```

Example WHMCS Cron Job

Since many hosting platforms (like WHMCS) rely heavily on PHP cron automation:
```
*/5 * * * * /usr/bin/php -q /home/whmcs/crons/cron.php
```

Conclusion

You now know how to create PHP cron jobs on Linux server.

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What are PHP Cron Jobs?

How to Create PHP Cron Jobs on Linux Server

Understanding Cron

Verify PHP CLI is Installed

Create a Basic PHP Cron Script

Editing the Crontab

Using Full Paths (Very Important)

Redirecting Output and Errors

PHP CLI Flags for Cron Jobs

Using the -c Flag (Custom php.ini)

Using the -d Flag (Override Settings)

Using the -q Flag

Using the -f Flag

Passing Arguments to PHP Scripts

Combining Flags and Arguments

Running PHP Inline with -r

Running as a Specific User

Locking Cron Jobs (Prevent Overlap)

Monitoring Cron Jobs

Example Production Cron Jobs

Queue Worker

Database Cleanup

Cache Purge

Backup Job

Security Best Practices

Use CLI PHP

Restrict Permissions

Avoid Running as Root

Log Everything

Example Enterprise PHP Cron Stack

Testing Cron Jobs Safely

Troubleshooting

Cron not running

PATH problems

Permission errors

Example WHMCS Cron Job

Conclusion

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Using the `-c` Flag (Custom php.ini)

Using the `-d` Flag (Override Settings)

Using the `-q` Flag

Using the `-f` Flag

Running PHP Inline with `-r`