从ExpressionEngine循环中删除JSON数组中的最后一个逗号

Question

我试图从这个ExpressionEngine循环创建一个JSON输出。它正在输出正确的JSON格式，但我似乎无法删除＆＃39;，＆＃39;在最后一个条目。

想知道删除此内容的最简单方法吗？

谢谢！

<?php
class TmeTbl {
    public $title = "";
    public $image  = "";
    public $day = "";
    public $start_time = "";
    public $end_time = "";
    public $timetable_studio = "";
    public $timetable_description = "";
}
?>

{
"items": [
{exp:channel:entries channel="timetable" limit="1"}
    {timetable}
        <?php
            $e = new TmeTbl();
            $e->title = "{title}";
            $e->image  = "{image}";
            $e->day  = "{day}";
            $e->start_time  = "{start_time}";
            $e->end_time  = "{end_time}";
            $e->timetable_studio  = "{studio}";
            $e->timetable_description  = "{timetable_description}";

            $json = json_encode($e).',';
            echo $json;
        ?>
    {/timetable}
{/exp:channel:entries}
]
}