php循环优化,循环优化PHP

我做了一个快速的基准：

$time = microtime();

$time = explode(' ', $time);

$time = $time[1] + $time[0];

$start = $time;

for ($count = 0; $count < 1000; $count++) {

for ($i=0;$i<10000;$i++);

}

$time = microtime();

$time = explode(' ', $time);

$time = $time[1] + $time[0];

$end = $time;

$diff = ($end - $start);

echo "Version 1 time: $diff seconds.";

$time = microtime();

$time = explode(' ', $time);

$time = $time[1] + $time[0];

$start = $time;

for ($count = 0; $count < 1000; $count++) {

for ($i=10000;$i--;);

}

$time = microtime();

$time = explode(' ', $time);

$time = $time[1] + $time[0];

$end = $time;

$diff = ($end - $start);

echo "Version 2 time: $diff seconds.";

?>

Test 1:

Version 1 time: 0.42717981338501 seconds.

Version 2 time: 0.46911406517029 seconds.

Test 2:

Version 1 time: 0.44191193580627 seconds.

Version 2 time: 0.46684908866882 seconds.

Test 3:

Version 1 time: 0.43247008323669 seconds.

Version 2 time: 0.46166205406189 seconds.击>

编辑

我再次做了基准测试，现在第二个版本更快了：

Test 1:

Version 1 time: 0.43037080764771 seconds.

Version 2 time: 0.29532289505005 seconds.

Test 2:

Version 1 time: 0.42874693870544 seconds.

Version 2 time: 0.29753398895264 seconds.

Test 3:

Version 1 time: 0.44300508499146 seconds.

Version 2 time: 0.2880539894104 seconds.实际上我发布了这个答案，因为我第一次得到了结果，而不是我的预期。但现在结果是应该的。

其他人解释的原因是与零比较执行得更快。