深入for,while,foreach遍历时间比较的详解

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这个是从别人空间里看来的，不过自己还真从来没这么做过他们三者之间的比较，今天也学习了一下。
复制代码 代码如下:
<?php
$arr = array();
for($i = 0; $i < 50000; $i++){
$arr[] = $i*rand(1000,9999);
}
function GetRunTime()
{
list($usec,$sec)=explode(" ",microtime());
return ((float)$usec+(float)$sec);
}
/*=============================================*/
$time_start = GetRunTime();
for($i = 0; $i < count($arr); $i++){
$str = $arr[$i];
}
$time_end = GetRunTime();
$time_used = $time_end - $time_start;
echo ''Used time of for:''.round($time_used, 7).''(s)<br /><br />'';
unset($str, $time_start, $time_end, $time_used);
/*=============================================*/
$time_start = GetRunTime();
while(list($key, $val) = each($arr)){
$str = $val;
}
$time_end = GetRunTime();
$time_used = $time_end - $time_start;
echo ''Used time of while:''.round($time_used, 7).''(s)<br /><br />'';
unset($str, $key, $val, $time_start, $time_end, $time_used);
/*=============================================*/
$time_start = GetRunTime();
foreach($arr as $key => $val){
$str = $val;
}
$time_end = GetRunTime();
$time_used = $time_end - $time_start;
echo ''Used time of foreach:''.round($time_used, 7).''(s)<br /><br />'';
?>