计算脚本运行时间(简易)

<?php
    //计算页面脚本时间,msec为微妙数
    function dist(){
        list($sec,$msec) = explode(" ",microtime());
        return $sec + $msec;
    }
    $start_time = dist();
    for($i=1;$i<100000;$i++){
        //
    }
    $end_time = dist();
    echo (round($end_time-$start_time,4));