double fork

php_daemon.php

<?php
/*
PHP forked daemon
Standalone PHP binary must be compiled with --enable-sockets and --enable-pcntl
Dave M. -2002
Online Services USA
*/
define(DEBUG,true);

require dirname(__FILE__)."/../../config/config.php";


$todo = $_SERVER['argv'][1];
$daemon = new svhost_daemon;

if ( $todo == 'start' ){
    $daemon->start();
}

if ( $todo == 'stop' ){
    $daemon->stop();
}

if ( $todo == 'restart' ){
    $daemon->stop();
    $daemon->start();
}

if ( $todo == 'status' ){
    $daemon->status();
}

if ( $todo == '' or !isset($todo) ){
    echo "usage: php daemon (start|stop|restart|status)\n";
}

class svhost_daemon{

    private $pid_file;
    private $sv_log_file;
    private $underpriv_uid;
    private $underpriv_gid;
    private $port;
    private $address;


    function __construct() {
        error_reporting (4);
        set_time_limit (0);
        ob_implicit_flush ();

        $this->pid_file = DATA_DIR.'/svhost.pid';
        $this->sv_log_file = DATA_DIR."/logs/svhost.log";

        $this->underpriv_uid = '99'; // uid 99 == user nobody, at least on my system.
        $this->underpriv_gid = '99';

        $this->port = '10000';
        $this->address = '127.0.0.1'; // 0 binds to all addresses, may not work on fbsd

        //pcntl_signal( SIGCHLD, array('this','sig_handler') );
        //pcntl_signal( SIGTERM, array('this','sig_handler') );
        //pcntl_signal( SIGINT, array('this','sig_handler') );
        pcntl_signal(SIGCHLD, SIG_IGN);

    }

    function __destruct(){
        if(!file_exists($this->pid_file)) {
            return;
        }

        if(posix_getpid() == $this->pid) {
            unlink($this->pid_file);
        }
    }

    function interact($connection) {
        $cid=getmypid();

        $msg = "\nWelcome to the PHP Execute Server. \n" .
            "To quit, type 'quit'. To shut down the server type 'shutdown'.\n";
        socket_write($connection, $msg, strlen($msg));

        while ( true ){   
            if (!is_resource($connection)){
                posix_kill($cid, SIGTERM);
                exit;
            }
            if (false === ($buf = socket_read($connection, 2048))) {
                next;
            }
            if ( substr($buf,0,4) == 'quit' ) {
                $talkback = "bye\n";
                socket_write($connection, $talkback, strlen($talkback));
                $this->sv_log ('Client Disconnect');
                posix_kill($cid, SIGTERM);
                exit;
            } elseif ( substr($buf,0,4) == 'exec' ) {
                $cmd = trim(substr($buf,5));
                $cmd = escapeshellcmd($cmd);
                $cmd = $cmd.' 2>&1 ';
                $this->sv_log( "exec $cmd" );
                $ret = @shell_exec ($cmd);
                if ( $ret == '' or !isset($ret)){
                    $ret = "$cmd exec failed";
                }
                $talkback = $ret."\n";
                if (DEBUG){
                    $this->sv_log( $ret );
                }
                socket_write($connection, $talkback, strlen($talkback));
            }else{
                $talkback = "Unknown command: " . str_replace("\r\n", '\r\n', $buf) ."\n";
                socket_write($connection, $talkback, strlen($talkback));
            }

            $buf = '';
        }
    }
 
    function start() {       

        if (($this->sock = socket_create (AF_INET, SOCK_STREAM, 0)) < 0) {
            $this->sv_log("socket_create() failed: reason: " . socket_strerror ($this->sock) );
        }

        if (($ret = socket_bind ($this->sock, $this->address, $this->port)) < 0) {
            $this->sv_log( "socket_bind() failed: reason: " . socket_strerror ($ret) );
        }

        if (($ret = socket_listen ($this->sock, 0)) < 0) {
            $this->sv_log( "socket_listen() failed: reason: " . socket_strerror ($ret) );
        }

        #change_identity($underpriv_uid,$underpriv_gid);

        $this->sv_log("Server ready. Waiting for connections.....");
        
        $fh = $this->open_pid_file($this->pid_file);
        $pid = $this->become_daemon();
        fputs($fh,$pid);
        fclose($fh);

  
        while(true ) {
            if (($connection = socket_accept($this->sock)) < 0) {
                next;
            }
            
            if( ($child = pcntl_fork()) == -1 ) {
                $this->sv_log("Could not fork!!");
                $this->sv_log("Dying...");
                exit;
            }
            elseif($child == 0) {
                $this->interact($connection);
                socket_close($this->sock); 
                exit;
            }else{
                pcntl_wait($status,1);
            }
            socket_close($connection);         
       }

       
    }

    function stop(){
        if(!file_exists($this->pid_file)) {
            $this->sv_log("PID file ".$this->pid_file." not found");
            exit;
        }
        $fp = fopen($this->pid_file,"r");
        $pid = fgets($fp,1024);
        if(!posix_kill($pid,9)) {
            $this->sv_log("can not kill PID: $pid");
            exit;
        }
        $this->sv_log("server process $pid stoped");
        if(!unlink($this->pid_file)) {
            $this->sv_log("Cannot unlink PID file ".$this->pid_file);
            exit;
        }
    }


    function status(){

    }


    function sig_handler($signo) {

         switch($signo) {
             case SIGTERM:
                 // handle shutdown tasks
                 exit;
                 break;
             case SIGHUP:
                 // handle restart tasks
                 break;
             case SIGUSR1:
                 $this->sv_log( "Caught SIGUSR1...");
                 break;
             case SIGCHLD:
                 while( pcntl_waitpid(-1,$status,WNOHANG)>0 ) { 
                 }
                 break;
             case SIGINT:
            exit;
             default:
                 // not implemented yet...
                 break;
         }

    }

    function sv_log($msg){
        $sv_log = date("Y-m-d H:i:s")." ".$msg."\r\n";
        error_log($sv_log,3,$this->sv_log_file);
    }



    function become_daemon() {

        $child = pcntl_fork();
        if($child) {
            exit; // kill parent
        }
        posix_setsid(); // become session leader
        chdir("/");
        umask(0); // clear umask
        return posix_getpid();

    }

    function open_pid_file($file) {

        if(file_exists($file)) {
            $fp = fopen($file,"r");
            $pid = fgets($fp,1024);
            fclose($fp);
            if(posix_kill($pid,0)) {
                $this->sv_log("Server already running with PID: $pid");
                exit;
            }
            $this->sv_log("Removing PID file for defunct server process $pid");
            if(!unlink($file)) {
                $this->sv_log("Cannot unlink PID file $file");
                exit;
            }
        }
        if($fp = fopen($file,"w")) {
            return $fp;
        } else {
            $this->sv_log( "Unable to open PID file $file for writing..." );
            exit;
        }
    }

    function change_identity($uid,$gid) {
        if(!posix_setgid($gid)) {
            $this->sv_log("Unable to setgid to $gid!");
            unlink($this->pid_file);
            exit;
        }    
        if(!posix_setuid($uid)) {
            $this->sv_log("Unable to setuid to $uid!");
            unlink($this->pid_file);
            exit;
        }  
    }
}