php – MySQL查询返回false值

这是我的代码：

<?php
class DataBase
{
    protected $dbUser;
    protected $dbPassword;
    protected $dbHost;
    protected $dbName;
    protected $db;

    function __construct()
    {
        $this->dbUser     = 'root';
        $this->dbPassword = '';
        $this->dbHost     = 'localhost';
        $this->dbName     = 'ecommercemakup';
        $this->db = mysqli_connect($this->dbHost,$this->dbUser,$this->dbPassword,$this->dbName) or die('Fatal error!');
    }

    public function getInstance()
    {
        return $this->db;
    }
}
?>

<?php
$db = new DataBase();
$r  = mysqli_query($db->getInstance(),"CALL categories()");
if (mysqli_num_rows($r) > 0) {
    while ($row = mysqli_fetch_array($r,MYSQLI_ASSOC)) {
        echo '<li> <a href=' . $row['name'] . '.php>';
        print_r($row['name']);
        echo '</a>
            <ul>';
        $id = intval($row['idCategory']);
        $r1 = mysqli_query($db->getInstance(),"CALL subcategories($id)");
        if (mysqli_num_rows($r1) > 0) {
            while ($row1 = mysqli_fetch_array($r1,MYSQLI_ASSOC)) {
                echo '<li><a href=' . $row1['name'],'.php>';
                print_r($row1['name']);
                echo '</a></li>';
            }
        }
        echo '</ul></li>';
    }
}
?>

第一个查询正确运行,但第二个查询始终返回false.

这两个程序是这样的：

DELIMITER @@
DROP PROCEDURE categories @@
CREATE PROCEDURE ecommercemakup.categories()
BEGIN
    SELECT * FROM categories;
END @@ 
DELIMITER ; 

DELIMITER @@
DROP PROCEDURE subcategories @@
CREATE PROCEDURE ecommercemakup.subcategories
(IN id_Category INT)
BEGIN
    SELECT idSubcategory,idCategory,name FROM subcategories WHERE idCategory = id_Category;
END @@ 
DELIMITER ;

类别表包含2个项目：idCategory和name,子类别表包含3个项目：idSubcategory,idCategory和name.

谁能告诉我这里做错了什么？