针对最大执行时间限制的基本保护

// initialize basic variables for further work
$maxexecutiontime = (int)ini_get('max_execution_time');
$estimatecycletime = 0;
$starttime = microtime(true);

// for demonstration purposes, we use an "infinite" loop with a simulated task lasting 10 seconds
while (true) {
   sleep(10);

   // calculate the current runtime
   $currentruntime = microtime(true) - $starttime;

   // termination can be done either with a fixed constant
   // or by measuring the time of one pass and trying to use
   // the longest possible segment of the runtime
   // limit (has its problem).
   if ($estimatecycletime === 0) {
       $estimatecycletime = $currentruntime;
   }

   // check if the iteration stop time is approaching.
   // subtract the time of one pass, which likely won't fit
   // within the window. 
   if (($maxexecutiontime - $estimatecycletime) < $currentruntime) {
       echo 'time is end';
       break;
   }
}

$beforeEndTime = 1;

if (($maxExecutionTime - $beforeEndTime) < $currentRunTime) {
    echo 'Time is end';
    break;
}