PHP多进程API
创建子进程
@params void@returns intint pcntl_fork(void)成功时，在父进程执行线程内返回产生的子进程PID，在子进程执行线程内返回0，失败时，在父进程上下文返回-1，不会创建子进程，并且会引发一个php错误获取当前进程id
@params void@returns intint posix_getpid(void)返回进程id，类型为整型父进程等待子进程退出
@params $status@params $option@return boolint pcntl_wait(int &$status[,int $options=0])该函数等同于以-1作为参数pid的值并且没有options参数来调用pcntl_waitpid()的函数进程退出状态
@params $status@return boolbool pcntl_wifexited(int $status)进程退出码
@params $status@return intint pcntl_wexitstatus(int $status)简单PHP多进程示例
function process_execute($input) { ???????$pid = pcntl_fork(); //创建子进程 ???????if ($pid == 0) {//子进程 ???????????????$pid = posix_getpid(); ???????????????echo "* Process {$pid} was created, and Executed:\n\n"; ???????????????eval($input); //解析命令 ???????????????exit; ???????} else {//主进程 ???????????????$pid = pcntl_wait($status, WUNTRACED); //取得子进程结束状态 ???????????????if (pcntl_wifexited($status)) { ???????????????????????echo "\n\n* Sub process: {$pid} exited with {$status}"; ???????????????} ???????}通过调用php创建子进程接口完成一个子进程的创建，pcntl_fork返回值为0证明进入到子进程内，非0则进入到父进程内部，-1则父进程创建子进程失败。
多个子进程初级版本示例
foreach ($clusterList as $key=>$value) { ???????????$pid = pcntl_fork();//创建子进程 ???????????if($pid == 0) {//子进程 ???????????????//do something ???????????} else if($pid == -1) { ???????????????//fork error occured ???????????} else { ???????????????pcntl_wait($status); ???????????} ???????}该实现方式主要逻辑为循环创建一个子进程，并且父进程等待子进程完成退出后，再继续创建下一个子进程
缺点：无法真正体现多进程，实际上时串行的创建子进程
多个子进程优化版本示例
foreach ($clusterList as $key=>$value) { ???????????$pid = pcntl_fork();//创建子进程 ???????????if($pid == 0) {//子进程 ???????????????//do something ???????????} else if($pid == -1) { ???????????????return false; ???????????} ???????} ???????for (;;) { ???????????$ret = pcntl_waitpid(-1,$status,WNOHANG); ???????????if ($ret == -1) { ???????????????// error occured ????????????} else if ($ret == 0) { ???????????????//all child are existed ???????????????break; ???????????} else { ???????????????//check sub process exit status ???????????????$extFlag = pcntl_wifexited($status); ???????????????if(!$extFlag){ ???????????????????//exited unnormally ???????????????}else { ???????????????????$extCode = pcntl_wexitstatus($status); ???????????????????//exited normally ???????????????} ???????????} ???????}该逻辑通过for循环不断获取子进程的退出状态，直到所有的子进程都退出，真正实现多进程处理。
php多进程编程实现与优化
原文地址：https://www.cnblogs.com/jingliming/p/9100309.html