for,while,foreach遍历时间比较

 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。

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<?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 />';?>