php include效率分析

<?php 
$time = microtime(true);
include_once './b.php';
$obj = new B();
for($i=0; $i<100000; ++$i) {
    $obj->fun();
}
echo microtime(true) - $time,'<br>';

$time1 = microtime(true);
for($i=0; $i<100000; ++$i) {
    include_once './b.php';
    $obj = new B();
    $obj->fun();
}
echo microtime(true) - $time1;

2.21210503578
5.32841205597

<?php
class B
{
    function fun()
    {
        ;;;;;;;;;
        ;;;;;;;;;
        ;;;;;;;;;
    }
}