PHP代码未从数据库中选择

Question

更新：用于计数的代码没有问题。连接到database

时只有一个拼写错误

$this->conn = new PDO("mysql:host=". $this->host . ";db_name=" . $this->db_name, $this->username, $this->password);

db_name应该是dbname。所以像

$this->conn = new PDO("mysql:host=". $this->host . ";dbname=" . $this->db_name, $this->username, $this->password);

我正在尝试将PHP REST api与mysql数据库一起使用，但这似乎不起作用，因为我首先尝试从我的select来database，但是尽管数据库中有记录，但这return仍然没有结果

下面是我的代码

database.php

<?php

class Database
{
    //Database Credentials
    private $host = "localhost";
    private $username = "root";
    private $password = "password";
    private $db_name = "rtmdb";

    public $conn;

    //Get Database Connection
    public function getConnection()
    {
        $this->conn = null;

        //Try connection
        try
        {
            $this->conn = new PDO("mysql:host=". $this->host . ";db_name=" . $this->db_name, $this->username, $this->password);
            $this->conn->exec("set names utf8");
        }
        catch(PDOException $exception)
        {
            echo "Connection error:" . $exception->getMessage();
        }

        return $this->conn;
    }
}

admin.php 从数据库中选择

<?php

class Admin
{
    //Database Connection and Table name
    private $conn;
    private $table_name = "admin";

    //object properties
    public $id;
    public $fname;
    public $lname;
    public $oname;
    public $uname;
    public $email;
    public $idnumber;
    public $password;
    public $profimage;
    public $datecreated;
    public $modifiedby;
    public $datemodified;
    public $status;

    //Construct $db as database connection

    public function __construct($db)
    {
        $this->conn = $db;
    }
    public function crawl()
    {
        $query = "SELECT * FROM " . $this->table_name; 

        $stmt = $this->conn->prepare($query);

        $stmt->execute();

        return $stmt;
    }
}

crawl.php 文件以获取数据和json_encode结果

//Include database and object files

include_once "../config/database.php";
include_once "../objects/admin.php";

$database = new Database();
$db = $database->getConnection();

$admin = new Admin($db);

//Query Admin
$stmt = $admin->crawl();
$num = $stmt->rowCount();

echo json_encode($num);
if($num > 0)
{

    while ($row = $stmt->fetch(PDO::FETCH_ASSOC))
    {
        extract($row);

        $admin_list = array(
            "id" => $id,
            "uname" => $uname
        );

        array_push($admin_arr['records'], $admin_list);

    }

    echo json_encode($admin_arr);
}
else
{
    echo json_encode(
        array("message" => "No registered admin found.")
    );
}

但是尽管有记录，我仍以rowCount()为0和“没有注册管理员”的身份

下面是我的表格结构的屏幕截图

数据库结构

我在数据库中也只有一个数据

但是这些似乎没有给我任何结果。请问什么问题以及如何解决？