安装最新windows版的；apache运行一会就报HTTP 500 - Internal Serv

<?php
ini_set("display_errors", "On");//打开错误提示
ini_set("error_reporting",E_ALL);//显示所有错误
set_time_limit(0);
include "./conndb.php";
$conndb=new conndb();
$conndb->connLocalhost();
$table="enterprise.info_member2";
$setIndex="info_member2";
$sql="select count(1) as num from ".$table."";
// echo $sql;
$res=$conndb->getOne($sql);
$conndb->close();
//上面可以运行
// print_r($res);exit();
if(!empty($res['num'])){
    $pageSize=50;
    $max=2;
    $j=1;
    for($i=1;$i<$max;$i++){
        $limitStart=($i-1)*$pageSize;
        $sql="select infoid,infounit,infoname from {$table} limit {$limitStart},{$pageSize}";
        $conndb->connLocalhost();
        $list=$conndb->select($sql);
        $conndb->close();
        //print_r($list);exit();
        //$list也有结果
        if(!empty($list)){
            //当$pageSize=10的时候可以运行到最后
            //当$pageSize=50的时候 foreach循环后就会报500错误
            foreach($list as $v){
                sleep(1);
                echo $j."<br />";
                $j++;
            }
        }
    }
}else{
    exit();
}
echo $sql;