登录系统,将mysqli转换为pdo错误

我正试图将一些MySQLi代码转换为Unity项目的PDO。我正在创建一个登录系统,我已经将MYSQLi的一些内容更改为PDO,但是在第33行出现了一个错误:

致命错误:调用未定义的方法PDOStatement::fetch_assoc()

我试图找到PDO版本的 fetch_assoc 发现这一点:

fetch(PDO::FETCH_ASSOC);

所以我把电话改成

while($row = $result->fetch(PDO::FETCH_ASSOC)) {

现在我的Unity DBcontroller有一个“Debug.Log(www.downloadHandler.text)”没有返回任何内容,登录消息也没有出现。。。你们这些巫师能告诉我下一步该去哪里吗?我想我应该说,当我使用MySQLi时,这个脚本运行得很好,但是我需要将它转换为这个项目的PDO。下面是代码:

<?php
$servername = "***";
$username = "***";
$password = "***";
$dbname = "***";

//variables submitted by user
$loginUser = $_POST["loginUser"];
$loginPass = $_POST["loginPass"];

// Create Connection
$conn = new PDO("mysql:host=***;dbname=***",
"***",
"***",
[PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);

//Check Connection
if(!$conn){
    die("Connection failed.");
}

$sql = "SELECT password FROM users WHERE username = '" . $loginUser . "'";

$result = $conn->query($sql);

if ($result->fetchAll() > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        if($row["password"] == $loginPass){
            echo "Login Success. Welcome ", $loginUser, "!";        
        }
        else{
            echo "Wrong Credentials.";
        }
    }
} else {
    echo "Username does not exist.";
}
$conn = null;

?>

if ($row = $result->fetch(PDO::FETCH_ASSOC)) { if($row["password"] == $loginPass){ echo "Login Success. Welcome ", $loginUser, "!"; } else{ echo "Wrong Credentials."; } } else { echo "Username does not exist."; }

$sql = "SELECT password FROM users WHERE username = :username"; $stmt = $conn->prepare($sql); $stmt->bindParam(':username', $loginUser); $stmt->execute(); if ($row = $stmt->fetch(PDO::FETCH_ASSOC)) { if(password_verify($loginPass, $row["password"])) { echo "Login Success. Welcome ", $loginUser, "!"; } else{ echo "Wrong Credentials."; } } else { echo "Wrong Credentials."; }