Apache – Request to launch background php script

If ever someone else is searching for a way to achieve this, here is the solution I found:

I call in Ajax a script, it forks itself and save the PID of the child process in the database. Then I call session_write_close() in the child process to allow user making new requests, and the father process exits (not waiting for child end). As the father exits, the user receive an answer to his request, and the child process continue his job.

Then in Ajax I call another script to get the evolution of the worker, and finally I get the result and kill the child process when everything is done.

Here is the code of my worker class:

class AsyncWorker
{
    private $pid;
    private $worker;

    private $wMgr;

    public function __construct($action, $content, $params = NULL)
    {
        $this->wMgr   = new WorkersManager();
        $pid = pcntl_fork(); // Process Fork
        if ($pid < 0) {
            Ajax::Response(AJX_ERR, "Impossible de fork le processus");
        } else if ($pid == 0) { // In the child, we start the job and save the worker properties
            sleep(1);
            $this->pid    = getmypid();
            $this->worker = $this->wMgr->fetchBy(array("pid" => $this->pid));
            if (!$this->worker) {
                $this->worker = $this->wMgr->getEmptyObject();
                $this->wMgr->create($this->worker);
            }
            $this->worker->setPid($this->pid);
            $this->worker->setAction($action);
            $this->worker->setContent($content);
            $this->worker->setPercent(0.00);
            $this->worker->setResult("");
            $this->wMgr->update($this->worker);
            $this->launch($params);
        } else { // In the father, we save the pid to DB and answer the request.
            $this->worker = $this->wMgr->fetchBy(array("pid" => $this->pid));
            if (!$this->worker) {
                $this->worker = $this->wMgr->getEmptyObject();
                $this->worker->setPid($pid);
                $this->wMgr->create($this->worker);
            }
            Ajax::Response(AJX_OK, "Worker started", $this->worker->getId());
        }
    }

    // Worker job
    private function launch($params = NULL)
    {
        global $form, $_PHPPATH, $url, $session;
        session_write_close(); // This is useful to let the user make new requests
        ob_start(); // Avoid writing anything

        /*
        ** Some stuff specific to my app (include the worker files, etc..)
        */            

        $result = ob_get_contents(); // Get the wrote things and save them to DB as result
        $this->worker->setResult($result);
        $this->worker->setPercent(100);
        ob_end_clean();
    }
}

It's a bit tricky but I had no choices, as I have no access to server plugins and libraries.