Is there a function similar to setTimeout() (JavaScript) for PHP?

There's the sleep function, which pauses the script for a determined amount of time.

See also usleep, time_nanosleep and time_sleep_until.

There is no way to delay execution of part of the code of in the current script. It wouldn't make much sense, either, as the processing of a PHP script takes place entirely on server side and you would just delay the overall execution of the script. There is sleep() but that will simply halt the process for a certain time.

You can, of course, schedule a PHP script to run at a specific time using cron jobs and the like.

PHP isn't event driven, so a setTimeout doesn't make much sense. You can certainly mimic it and in fact, someone has written a Timer class you could use. But I would be careful before you start programming in this way on the server side in PHP.

A few things I'd like to note about timers in PHP:

1) Timers in PHP make sense when used in long-running scripts (daemons and, maybe, in CLI scripts). So if you're not developing that kind of application, then you don't need timers.

2) Timers can be blocking and non-blocking. If you're using sleep(), then it's a blocking timer, because your script just freezes for a specified amount of time. For many tasks blocking timers are fine. For example, sending statistics every 10 seconds. It's ok to block the script:

while (true) {
    sendStat();
    sleep(10);
}

3) Non-blocking timers make sense only in event driven apps, like websocket-server. In such applications an event can occur at any time (e.g incoming connection), so you must not block your app with sleep() (obviously). For this purposes there are event-loop libraries, like reactphp/event-loop, which allows you to handle multiple streams in a non-blocking fashion and also has timer/ interval feature.

4) Non-blocking timeouts in PHP are possible. It can be implemented by means of stream_select() function with timeout parameter (see how it's implemented in reactphp/event-loop StreamSelectLoop::run()).

5) There are PHP extensions like libevent, libev, event which allow timers implementation (if you want to go hardcore)