Use PHP to create, edit and delete crontab jobs?

Question

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.

We recently prepared a mini project (PHP>=5.3) to manage the cron files for private and individual tasks. This tool connects and manages the cron files so you can use them, for example per project. Unit Tests available :-)

Sample from command line:

bin/cronman --enable /var/www/myproject/.cronfile --user www-data

Sample from API:

use php\manager\crontab\CrontabManager;

$crontab = new CrontabManager();
$crontab->enableOrUpdate('/tmp/my/crontab.txt');
$crontab->save();

Managing individual tasks from API:

use php\manager\crontab\CrontabManager;

$crontab = new CrontabManager();
$job = $crontab->newJob();
$job->on('* * * * *');
$job->onMinute('20-30')->doJob("echo foo");
$crontab->add($job);
$job->onMinute('35-40')->doJob("echo bar");
$crontab->add($job);
$crontab->save();

github: php-crontab-manager

Check a cronjob

function cronjob_exists($command){

    $cronjob_exists=false;

    exec('crontab -l', $crontab);


    if(isset($crontab)&&is_array($crontab)){

        $crontab = array_flip($crontab);

        if(isset($crontab[$command])){

            $cronjob_exists=true;

        }

    }
    return $cronjob_exists;
}

Append a cronjob

function append_cronjob($command){

    if(is_string($command)&&!empty($command)&&cronjob_exists($command)===FALSE){

        //add job to crontab
        exec('echo -e "`crontab -l`\n'.$command.'" | crontab -', $output);


    }

    return $output;
}

Remove a crontab

exec('crontab -r', $crontab);

Example

exec('crontab -r', $crontab);

append_cronjob('* * * * * curl -s http://localhost/cron/test1.php');

append_cronjob('* * * * * curl -s http://localhost/cron/test2.php');

append_cronjob('* * * * * curl -s http://localhost/cron/test3.php');

This should do it

shell_exec("crontab -l | { cat; echo '*/1    *    *    *    *    command'; } |crontab -");

I tried the solution below

class Crontab {

// In this class, array instead of string would be the standard input / output format.

// Legacy way to add a job:
// $output = shell_exec('(crontab -l; echo "'.$job.'") | crontab -');

static private function stringToArray($jobs = '') {
    $array = explode("\r\n", trim($jobs)); // trim() gets rid of the last \r\n
    foreach ($array as $key => $item) {
        if ($item == '') {
            unset($array[$key]);
        }
    }
    return $array;
}

static private function arrayToString($jobs = array()) {
    $string = implode("\r\n", $jobs);
    return $string;
}

static public function getJobs() {
    $output = shell_exec('crontab -l');
    return self::stringToArray($output);
}

static public function saveJobs($jobs = array()) {
    $output = shell_exec('echo "'.self::arrayToString($jobs).'" | crontab -');
    return $output; 
}

static public function doesJobExist($job = '') {
    $jobs = self::getJobs();
    if (in_array($job, $jobs)) {
        return true;
    } else {
        return false;
    }
}

static public function addJob($job = '') {
    if (self::doesJobExist($job)) {
        return false;
    } else {
        $jobs = self::getJobs();
        $jobs[] = $job;
        return self::saveJobs($jobs);
    }
}

static public function removeJob($job = '') {
    if (self::doesJobExist($job)) {
        $jobs = self::getJobs();
        unset($jobs[array_search($job, $jobs)]);
        return self::saveJobs($jobs);
    } else {
        return false;
    }
}

}

credits to : Crontab Class to Add, Edit and Remove Cron Jobs