Daemonizing a PHP script without pcntl_fork()

I'm working on an embedded system that is programmed with PHP 4.4.9 - unfortunately without the PCNTL extension.

I need to create a script that runs in the background as a daemon. You'd usually do this using fork(), or in the PHP case, pcntl_fork() - but this function is not avai开发者_StackOverflow社区lable. A shell is also missing, so I can't use the standard tools.

So, what other ways are there to cleanly start a process in the background?

As kingCrunch says, you really should upgrade.

Firstly, there's more to making a daemon than just calling pcntl_fork(). You might want to read the Unix programming FAQ and the Unix socket FAQ.

Next, you've not mentioned how you intend to solve the problem of concurrency - while forking is one solution to this it is not the only reason for using fork() in a daemon.

So you've really got 2 problems to solve, first how you daemonize the program then how you handle concurrency.

Note that one approach to the latter which obviates the former is to run the server from [x]inetd.

Another approach to solving the concurrency problem is to run a single threaded server and use socket_select (or stream_select) to multiplex the connections - but I'm not sure how well that is supported in PHP 4 - there is a good example here.

A simple solution would be to write a simple wrapper program in C using daemon() to bootstrap the program. Or you could start it up directly from inittab. Or for a solution with complex management facilities have a look at DJB's daemontools