我写了一个检查剩余执行时间的函数。

警告:执行时间计数在Windows和Linux平台上是不同的。

/**
 * Check if more that `$miliseconds` ms remains
 * to error `PHP Fatal error:  Maximum execution time exceeded`
 * 
 * @param int $miliseconds
 * @return bool
 */
function isRemainingMaxExecutionTimeBiggerThan($miliseconds = 5000) {
    $max_execution_time = ini_get('max_execution_time');
    if ($max_execution_time === 0) {
        // No script time limitation
        return true;
    }
    if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
        // On Windows: The real time is measured.
        $spendMiliseconds = (microtime(true) - $_SERVER["REQUEST_TIME_FLOAT"]) * 1000;
    } else {
        // On Linux: Any time spent on activity that happens outside the execution
        //           of the script such as system calls using system(), stream operations
        //           database queries, etc. is not included.
        //           @see http://php.net/manual/en/function.set-time-limit.php
        $resourceUsages = getrusage();
        $spendMiliseconds = $resourceUsages['ru_utime.tv_sec'] * 1000 + $resourceUsages['ru_utime.tv_usec'] / 1000;
    }
    $remainingMiliseconds = $max_execution_time * 1000 - $spendMiliseconds;
    return ($remainingMiliseconds >= $miliseconds);
}

使用:

while (true) {
    // so something

    if (!isRemainingMaxExecutionTimeBiggerThan(5000)) {
        // Time to die.
        // Safely close DB and done the iteration.
    }
}

talal7860回答的简短版本

<?php
// At start of script
$time_start = microtime(true); 

// Anywhere else in the script
echo 'Total execution time in seconds: ' . (microtime(true) - $time_start);

正如所指出的，这是“wallclock时间”而不是“cpu时间”

进一步扩展Hamid的回答，我写了一个可以重复启动和停止的helper类(用于在循环中进行分析)。

   class ExecutionTime
   {
      private $startTime;
      private $endTime;
      private $compTime = 0;
      private $sysTime = 0;

      public function Start(){
         $this->startTime = getrusage();
      }

      public function End(){
         $this->endTime = getrusage();
         $this->compTime += $this->runTime($this->endTime, $this->startTime, "utime");
         $this->systemTime += $this->runTime($this->endTime, $this->startTime, "stime");
      }

      private function runTime($ru, $rus, $index) {
         return ($ru["ru_$index.tv_sec"]*1000 + intval($ru["ru_$index.tv_usec"]/1000))
         -  ($rus["ru_$index.tv_sec"]*1000 + intval($rus["ru_$index.tv_usec"]/1000));
      }

      public function __toString(){
         return "This process used " . $this->compTime . " ms for its computations\n" .
                "It spent " . $this->systemTime . " ms in system calls\n";
      }
   }

当PHP中有闭包功能时，为什么我们不从中获益呢?

function startTime(){
    $startTime = microtime(true);
    return function () use ($startTime){
        return microtime(true) - $startTime;
    };
}

现在，在上述函数的帮助下，我们可以像这样跟踪时间

$stopTime = startTime();
//some code block or line
$elapsedTime = $stopTime();

每次调用startTime函数都会启动一个单独的时间跟踪器。所以你可以想启动多少就启动多少，也可以在任何你想要的地方停止它们。

developerfusion.com的Gringod给出了一个很好的答案:

<!-- put this at the top of the page --> 
<?php 
   $mtime = microtime(); 
   $mtime = explode(" ",$mtime); 
   $mtime = $mtime[1] + $mtime[0]; 
   $starttime = $mtime; 
;?> 

<!-- put other code and html in here -->


<!-- put this code at the bottom of the page -->
<?php 
   $mtime = microtime(); 
   $mtime = explode(" ",$mtime); 
   $mtime = $mtime[1] + $mtime[0]; 
   $endtime = $mtime; 
   $totaltime = ($endtime - $starttime); 
   echo "This page was created in ".$totaltime." seconds"; 
;?>

从(http://www.developerfusion.com/code/2058/determine-execution-time-in-php/)

您可能只想知道部分脚本的执行时间。为部分或整个脚本计时的最灵活的方法是创建3个简单的函数(这里给出了过程代码，但您可以通过在它周围放置类timer{}并进行一些调整将其转换为类)。这段代码工作，只需复制粘贴并运行:

$tstart = 0;
$tend = 0;

function timer_starts()
{
global $tstart;

$tstart=microtime(true); ;

}

function timer_ends()
{
global $tend;

$tend=microtime(true); ;

}

function timer_calc()
{
global $tstart,$tend;

return (round($tend - $tstart,2));
}

timer_starts();
file_get_contents('http://google.com');
timer_ends();
print('It took '.timer_calc().' seconds to retrieve the google page');