How does php implement user-defined timing tasks

  node.js, question

One problem encountered is:

User A sets a scheduled task to be executed at 9: 00 a.m. every morning after logging in the background.
 User B sets a scheduled task to be executed at 8: 00 every night after logging in the background.
 User c
    ...
  
 How is this function designed
 Users are users of web systems, not users of operating systems.

 

After the user sets the timing task, the background logic issues the timing task tocrontab, usecrontabTo execute the user’s task regularly.