PHP mysql選擇MAX（）

Question

嘗試在PHP MySQL選擇MAX() ，但未顯示任何結果，也未顯示錯誤（錯誤顯示為on

error_reporting(E_ALL);
ini_set('display_errors', 1);

）。

我試過了：

$user_home = new USER();

$select_max = $user_home->runQuery("SELECT MAX(Gems) AS highest FROM users"); 
$get_max = $select_max->fetch(PDO::FETCH_ASSOC); 
$highest = $get_max['highest'];
echo $highest;

類文件：

public function __construct()
    {
        $database = new Database();
        $db = $database->dbConnection();
        $this->conn = $db;
    }

    public function runQuery($sql)
    {
        $stmt = $this->conn->prepare($sql);
        return $stmt;
    }

Answer 1

您不執行查詢，只是准備查詢並獲取數據...

$select_max = $user_home->runQuery("SELECT MAX(Gems) AS highest FROM users"); 
$select_max->execute();
$get_max = $select_max->fetch(PDO::FETCH_ASSOC); 
$highest = $get_max['highest'];
echo $highest;