I am trying set cron job from php code:
file_put_contents('mycrontab.txt', '* * * * * /usr/bin/php /home2/blabla/public_html/executable_file.php');
echo exec('crontab mycrontab.txt');
The above code not starts cron job, because when I am trying get current cron jobs
var_dump( shell_exec("crontab -l") );
result is NULL
P.S. Sorry if this question is very dumb, I am not know almost nothing about linux commands, including cron jobs.