最近个人项目中需要后台运行任务，之前一直是用nouhp & + 重定向输出 来后台跑任务，后来觉得不好维护原始数据，同时可能也没有直接操作进程那么稳吧（没验证）。废话少说，来看分析。
首先，我们守护进程的主要目的是创建一个长生存期的进程，独立于控制端去完成你设置的任务，与此同时可以加入事件监听或者 状态轮询，构成一个完整的运行机制
php中使用pcntl_fork()来 创建子进程，如下程序会在父进程和子进程中分别运行，区别是返回的pid不一样：
$pid = pcntl_fork();if ($pid == -1) { 创建失败 ???// 当 pid 为 -1 的时候表示创建子进程失败，这时返回-1。 ???return false;} else if ($pid) {//这里运行的是父进程，但是pid 指的是他的子进程pid ???} else { //pid 为0 的时候，说明运行的子进程}以上你需要 想象着 在不同的通道里去执行代码，进程只是计算机操作系统初期提出来一个形象化的概念，包括后面更加粒度更细化的线程。
需要注意的是 ，你想要独立出来完成任务，那么就不再依赖原来的环境了，包括目录，上下文环境，
这个时候我需要 php提供了 一些 set方法，用来设置进程的上下文环境，如下：
posix_setsid(); chdir("/")
可参考http://php.net/manual/zh/function.posix-setsid.php
接着 为了让进程便于我们控制并稳定的运行，我利用了 linux系统里面的信号，通过信号来处理 相应的操作，
对于php提供的安装信号的操作函数，可以使用 ?pcntl_signal()，http://php.net/manual/zh/function.pcntl-signal.php
对于信号的参考可以查看一下文章：http://www.cnblogs.com/guixiaoming/p/7700132.html
使用的例子（强行停止）：posix_kill($pid, SIGKILL)
最后就是一些异常处理，以下是我的个人项目中使用的守护进程：
abstract class DaemonBase{ ???const LOG_ECHO = 1; ???const LOG_FILE = 2; ???/** ????* @var $child_pid 子进程的pid ????*/ ???public $child_pid; ???public $pid_file; ???public $log_file; //每个子类的日志文件 ???public $switch = true; //开关 ???????public $cnt; //重启的计数 ???public $do_works = []; ????public $sig_handlers = []; ???/** ????* 配置 ????*/ ???public static $config = [ ???????‘current_dir‘ ?=> ‘‘, ???????‘log_file‘ ????=> ‘/tmp/‘ . __CLASS__ . ‘.log‘, ???????‘pid‘ ?????????=> ‘/tmp/‘ . ‘daemon‘ . ‘.pid‘, ???????‘limit_memory‘ => -1, //分配最大内存 ???????‘max_times‘ ???=> 0, //重启的最大次数 ???]; ???/** ????* 构造函数，设置path.以及注册shutdown ????*/ ???public function __construct() ???{ ???????$this->pid_file = ‘/tmp/‘ . get_class($this) . ‘.pid‘; ???????$this->log_file = ‘/tmp/‘ . get_class($this) . ‘.log‘; ???????set_error_handler([$this, ‘errorHandler‘]); ???????register_shutdown_function(array($this, ‘shutdown‘)); ???????ini_set(‘memory_limit‘, self::$config[‘limit_memory‘]); ???????ini_set(‘display_errors‘, ‘Off‘); ???????clearstatcache(); ???} ???/** ????* 执行启动程序 ????* @param string $command ????*/ ???public function run($command = ‘start‘) ???{ ???????if(empty($command) || !in_array($command, [‘start‘, ‘stop‘, ‘restart‘, ‘status‘])){ ???????????$command = ‘help‘; ???????} ???????$this->$command(); ???} ???/** ????* 开始 ????*/ ???public function start() ???{ ???????$this->log(‘Starting daemon...‘, self::LOG_ECHO | self::LOG_FILE); ???????$this->daemonize(); ??????echo ‘Daemon #‘ . $this->getChildPid() . ‘ 启动成功‘ .PHP_EOL; ???????declare(ticks = 1){ ???????????while($this->switch){ ???????????????$this->autoRestart(); ???????????????$this->todo(); ???????????????try { ???????????????????????????????????????$this->main(); ???????????????}catch (Exception $e) { ???????????????????var_dump($e); ???????????????????$this->log($e->getMessage(), self::LOG_FILE); ???????????????} ???????????} ???????} ???} ???/** ????* 停止 ????*/ ???public function stop() ???{ ???????if (!$pid = $this->getChildPid()) { ???????????$this->log(‘守护进程 GG‘, self::LOG_FILE); ???????????exit(); ???????} ???????posix_kill($pid, SIGKILL); ???} ???protected function stopAll() ???{ ???????if (!is_writeable($this->log_file)) { ???????????$this->log(‘Daemon (no pid file) not running‘, self::LOG_ECHO); ???????????return FALSE; ???????} ???????$pid = $this->getChildPid(); ???????unlink($this->log_file); ???????$this->log(‘Daemon #‘ . $pid . ‘ has stopped‘, self::LOG_ECHO | self::LOG_FILE); ???????$this->switch = TRUE; ???} ???public function restart() ???{ ???????if (!$pid = $this->getChildPid()) { ???????????$this->log(‘守护进程 GG‘, self::LOG_FILE); ???????????exit(); ???????} ???????posix_kill($pid, SIGHUP); ???} ???public function status() ???{ ???????if($pid = $this->getChildPid()) { ???????????$msg = "pid: $pid is running"; ???????}else { ???????????$msg = "进程GG"; ???????} ???????$this->log($msg, self::LOG_ECHO); ???} ???/** ????* 帮助命令 ????*/ ???public function help() ???{ ???????echo ‘start | stop | status | restart‘; ???} ???/** ????* 检测能否正常启动 ????* @return bool ????*/ ???protected function check() ???{ ???????if ($pid = $this->getChildPid()) { ???????????$this->log("Daemon #{$pid} has already started", self::LOG_ECHO); ???????????return FALSE; ???????} ???????$dir = dirname(self::$config[‘pid‘]); ???????if (!is_writable($dir)) { ???????????$this->log("you do not have permission to write pid file @ {$dir}", self::LOG_ECHO); ???????????return FALSE; ???????} ???????if (!is_writable(self::$config[‘log_file‘]) || !is_writable(dirname(self::$config[‘log_file‘]))) { ???????????$this->log("you do not have permission to write log file: {log_file}", self::LOG_ECHO); ???????????return FALSE; ???????} ???????if (!defined(‘SIGHUP‘)) { // Check for pcntl ???????????$this->log(‘PHP is compiled without --enable-pcntl directive‘, self::LOG_ECHO | self::LOG_FILE); ???????????return FALSE; ???????} ???????if (‘cli‘ !== php_sapi_name()) { // Check for CLI ???????????$this->log(‘You can only create daemon from the command line (CLI-mode)‘, self::LOG_ECHO | self::LOG_FILE); ???????????return FALSE; ???????} ???????if (!function_exists(‘posix_getpid‘)) { // Check for POSIX ???????????$this->log(‘PHP is compiled without --enable-posix directive‘, self::LOG_ECHO | self::LOG_FILE); ???????????return FALSE; ???????} ???????return TRUE; ???} ???/** ????* 创建子进程，并做好信号处理工作 ????*/ ???protected function daemonize() ???{ ???????//检查状态 ???????$this->check(); ???????//fork 子进程 ???????$this->fork(); ???????//信号处理 ???????$sig_array = [ ???????????SIGTERM => [$this, ‘defaultSigHandler‘], ???????????SIGQUIT => [$this, ‘defaultSigHandler‘], ???????????SIGINT ?=> [$this, ‘defaultSigHandler‘], ???????????SIGHUP ?=> [$this, ‘defaultSigHandler‘], ???????]; ???????foreach ($sig_array as $signo => $callback) { ???????????pcntl_signal($signo, $callback); ???????} ??????file_put_contents($this->pid_file, $this->child_pid); ???} ???/** ????* fork 子进程 ????* @return bool ????*/ ???protected function fork() ???{ ???????$pid = pcntl_fork(); ???????if($pid == -1) { //创建子进程失败 ???????????return false; ???????} ???????if($pid) { // 父进程 ???????????exit(); ???????} ???????//子进程 ???????$this->child_pid = posix_getpid(); //子进程id ???????posix_setsid(); //使进程成为会话组长,让进程摆脱原会话的控制；让进程摆脱原进程组的控制； ???????return true; ???} ???/** ????* 重启 ????*/ ???protected function autoRestart() ???{ ???????if((self::$config[‘max_times‘] && $this->cnt >= self::$config[‘max_time‘]) || ???????????(0 !== self::$config[‘limit_memory‘] && memory_get_usage(TRUE) >= self::$config[‘limit_memory‘])) ???????{ ???????????$this->doworks = [[$this, ‘restart‘]]; ???????????$this->cnt = 0; ???????} ???????$this->cnt++; ???} ???public function getChildPid(){ ???????if(!file_exists($this->pid_file)){ ???????????return false; ???????} ???????$pid = (int)file_get_contents($this->pid_file); ???????return file_exists("/proc/{$pid}") ? $pid : FALSE; //检测是否确实存在此进程 ???} ???public function todo() ???{ ???????foreach ($this->do_works as $row) { ???????????(1 === count($row)) ? call_user_func($row[0]) : call_user_func_array($row[0], $row[1]); ???????} ???} ???/** ????* 需要执行的逻辑体 ????* ????* @return mixed ????*/ ???abstract public function main(); ???public function defaultSigHandler($signo) ???{ ???????switch ($signo) { ???????????case SIGTERM: ???????????case SIGQUIT: ???????????case SIGINT: ???????????????$this->do_works = [[$this, ‘stop‘]]; ???????????????break; ???????????case SIGHUP: ???????????????$this->do_works = [[$this, ‘restart‘]]; ???????????????break; ???????????default: ???????????????break; ???????} ???} ???/** ????* Regist signo handler ????* ????* @param int $sig ????* @param callback $action ????*/ ???public function regSigHandler($sig, $action) ???{ ???????$this->sig_handlers[$sig] = $action; ???} ???public function errorHandler($error_code, $msg){ ???} ???/** ????* 守护进程日志 ????* ????* @param string $msg ????* @param int $io, 1->just echo, 2->just write, 3->echo & write ????*/ ???public function log($msg, $io = self::LOG_FILE) ???{ ???????$datetime = date(‘Y-m-d H:i:s‘); ???????$msg = "[{$datetime}] {$msg}\n"; ???????if ((self::LOG_ECHO & $io) && !$this->child_pid) { ???????????echo $msg, "\n"; ???????} ???????if (self::LOG_FILE & $io) { ???????????file_put_contents($this->log_file, $msg, FILE_APPEND | LOCK_EX); ???????} ???} ???/** ????* 脚本跑完执行 ????*/ ???public function shutdown() ???{ ???????if ($error = error_get_last()) { ???????????$this->log(implode(‘|‘, $error), self::LOG_FILE); ???????} ???????if (is_writeable(self::$config[‘pid‘]) && $this->child_pid) { ???????????unlink(self::$config[‘pid‘]); ???????} ???}php 守护进程类
原文地址：http://www.cnblogs.com/guixiaoming/p/7716709.html