我调用函数时，我的PHP文件没有显示出来

Question

代码：

<?php
require 'Controllers/MenuController.php';
$menuController = new MenuController();
if(isset($_POST['types']))
{
    $menuTables = $menuController->CreateTypeTables($_POST['types']);
}
else 
{
    $menuTables = $menuController->CreateTypeTables("%");
}
$title = 'Menus';
$content = $menuController->CreateMenuDropdownList(). $menuTables;
include 'Template.php';
?>

基本上当我这样做的时候，我的页面没有任何东西，甚至没有回声

它甚至没有显示我的css背景图片

但是当我排除这个功能时：

    <?php
    require 'Controllers/MenuController.php';
    $menuController = new MenuController();
   // if(isset($_POST['types']))
   //{
   //     $menuTables = $menuController->CreateTypeTables($_POST['types']);
   // }
   // else 
   // {
   //     $menuTables = $menuController->CreateTypeTables("%");
   // }
    $title = 'Menus';
    $content = "test";
   //$menuController->CreateMenuDropdownList() . $menuTables;
    include 'Template.php';
    ?>

它显示了我的背景图片和内容; '测试'。

我认为我的功能出了问题，但我对它们进行了三重检查

Sooooo帮助！

这是MenuController.php文件;

<?php
require ("Model/MenuModel.php");
class MenuController {
   function CreateMenuDropdownList(){
        $menuModel = new MenuModel();
        $result = "<form action = '' method = 'post' width = 200px'>
            Type:
            <select name = 'types' >
            <option value = '%' >All</option>
            ".$this->CreateOptionValues($menuModel->GetMenuTypes()).
                "</select>
                <input type = 'submit' value = 'Search' />
                </form>";
        return $result;
    }
    function CreateOptionValues(array $types){
     $result = "";
     foreach ($types as $type){
         $result = $result . "<option value='$type'>$type</option>";
     }
     return $result;
    }


    function  CreateTypeTables($types){
        $menuModel = new MenuModel();
    $menuArray = $menuModel->GetItemsByType($types);
    $result = "";
    foreach ($menuArray as $key => $product){
        $result = $result .
                "
                    <table class = 'coffeeTable'>
                <tr>
                <th></th>
                        <th>Name: </th>
                    <td>$product->desc</td>
                <tr>

                <tr>
                <th></th>
                        <th>Type: </th>
                    <td>$product->type</td>
                <tr>

                <tr>
<th></th>
                        <th>Price: </th>
                    <td>$product->price</td>
                <tr>

                <form  method='post'>
    <button type='submit' name='insert' value='$product->id' class='button1'>Add</button>
    </form>
                    </table>";
    }
    return $result;
    }


}