# Program execution splits here:
if ($kidPID=fork()) {
    # On return from fork, the parent is in this branch of the if statement
    do {
        # Keep checking for child process to end.  (Probably ought to put in
        # a sleep so we don't just sit and pound the CPU while we're waiting)
        $kidPID = waitpid($kidPID, WNOHANG);
    } while $kidPID > 0;
    # Child is done now, so continue onwards
}
else {
    # On return from fork, the child process is in this branch
    exec($your_batch_file);
}