Use PHP to create, edit and delete crontab jobs?

Question

Is it possible to use PHP to create, edit and delete crontab jobs?

I know how to list the current crontab jobs of the Apache user:

$output = shell_exec('crontab -l');
echo $output;

But how to add a cron job with PHP? 'crontab -e' would just open a text editor and you will have to manually edit the entries before saving the file.

And how to delete a cron job with PHP? Again you have to manually do this by 'crontab -e'.

With a job string like this:

$job = '0 */2 * * * /usr/bin/php5 /home/user1/work.php';

How do I add it to the crontab jobs list with PHP?

Answer 1

crontab command usage

usage:  crontab [-u user] file
        crontab [-u user] [ -e | -l | -r ]
                (default operation is replace, per 1003.2)
        -e      (edit user's crontab)
        -l      (list user's crontab)
        -r      (delete user's crontab)
        -i      (prompt before deleting user's crontab)

So,

$output = shell_exec('crontab -l');
file_put_contents('/tmp/crontab.txt', $output.'* * * * * NEW_CRON'.PHP_EOL);
echo exec('crontab /tmp/crontab.txt');

The above can be used for both create and edit/append provided the user has the adequate file write permission.

To delete jobs:

echo exec('crontab -r');

Also, take note that apache is running as a particular user and that's usually not root, which means the cron jobs can only be changed for the apache user unless given crontab -u privilege to the apache user.