登录验证

<?php

    $serverName = "localhost";
    $username = "root";
    $password = "123456";
    $dataBase = "yunhu";

    $conn = new mysqli($serverName, $username, $password,$dataBase);

    if($conn->connect_error) {
        echo "error";
        echo "<br>";
    }

    $sql = "SET NAMES UTF8";
    if($conn->query($sql) === true) {
        echo "set success<br>";
    }
    else {
        echo "set fail<br>";
    }

    $username_post = $_POST['username'];
    $password_post = $_POST['password'];
    $result = array();

    $stmt = $conn->prepare("SELECT username,password FROM userInformation WHERE username=?");
    $stmt->bind_param("s", $username_post);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($username_db,$password_db);

    if($stmt->fetch()) {
        if(($username_db == $username_post) && ($password_db == $password_post)) {
            echo "登录成功";
        }
        else {
            echo "登录失败";
        }
    }
    else {
        echo "mengbi";
    }
   // echo $result["result"];
?>