我要用php读取 C:\phpStudy\PHPTutorial\WWW\user_info 文件夹里面的图片并显示在页面上去

$.ajax({
        type:"post",
        url:"blogs_showpics_href.php",
        data:datas,
        dataType:"json",
        success:function(result){
            alert(result);
        },
        error:function(){
            alert("内部服务器错误");
        }
    });




<?php
    $a = $_POST['ids'];
    $hostdir = dirname(__FILE__)."phpStudy\PHPTutorial\WWW\user_info\photo\ $a";
    $url = "phpStudy\PHPTutorial\WWW\user_info\photo\ $a";
    $filesnames = scandir($hostdir);
    print_r ($filesnames);
//    $www = 'http://www.***.com/';
//    foreach($filesnames as $name){
//        $aurl= "<img width='100' height='100' src='"$url."10.jpg"."' alt = '".$name."'>"
//    }
//    echo $filesnames;
    echo json_encode($hostdir);
?>


为什么老是执行不成功啊