Backbone 无法fetch,大家给看看啥原因呢

fetch.php：

<?php

$stulist = array (
    array("Code" => "10101", "Name" => "张三", "Score" => "530"),
    array("Code" => "10102", "Name" => "李自强", "Score" => "360"),
    array("Code" => "10103", "Name" => "郑中华", "Score" => "170"),
    array("Code" => "10104", "Name" => "王大亮", "Score" => "216"),
    array("Code" => "10105", "Name" => "薛宝钗", "Score" => "313")
);

echo json_encode($stulist);

?>

var student = Backbone.Model.extend({
    defaults: {
        Code: "",
        Name: "",
        Score: 0
    },
    idAttribute: "Code"
});

var stulists = Backbone.Collection.extend({
    initialize: function(){
        console.log("-------------reset shijian chufa ----------");
        this.on("reset", function(render){
            for(var i = 0; i < render.models.length; i++){
                console.log(render.models[i].toJSON());
            }

        });

    },
    model: student,
    url: "./api/resources/fetch.php"
});


var stus = new stulists();

console.log(" =================================================");

stus.fetch({
    reset: true,
    success: function(collection, resp, option){
        console.log("---------- success -----------");
        for(var i=0; i < collection.models.length; i++){
            console.log(collection.models[i].toJSON());
        }

    },
    error: function(a,b,c){

        console.log("-============== error ===========");

        console.log(a);
        console.log(b);
        console.log(c);
    }
})