我当前正在制作一个登录表单，但是由于某种原因，与数据库的连接无法正常工作。有人知道代码有什么问题吗？我将在下面发布我的意思。我在学习如何使用PHP时将其作为练习。这是我尝试注册时遇到的错误：
注册由于服务器错误而失败。请稍后再试
config.php
<?php
$hostname = 'localhost';
$username = 'root';
$password = '';
$databaseName = '508658';
//Open the database connection - exit with error message otherwise
$connection = mysqli_connect($hostname, $username, $password, $databaseName) or exit("Unable to connect to database!");
?>
registration.php
<?php
session_start();
include ('config.php');
//phpinfo();
?>
<!DOCTYPE html>
<html>
<head>
<title>Sign Up Page</title>
<link rel="stylesheet" href="css/style.css">
</head>
<body style="background-color:#bdc3c7">
<div id="main-wrapper">
<center><h2>Sign Up Form</h2></center>
<form action="register.php" method="post">
<div class="imgcontainer">
<img src="imgs/avatar.png" alt="Avatar" class="avatar">
</div>
<div class="inner_container">
<label><b>Username</b></label>
<input type="text" placeholder="Enter Username" name="username" required>
<label><b>Password</b></label>
<input type="password" placeholder="Enter Password" name="password" required>
<label><b>Confirm Password</b></label>
<input type="password" placeholder="Enter Password" name="cpassword" required>
<button name="register" class="sign_up_btn" type="submit">Sign Up</button>
<a href="index.php"><button type="button" class="back_btn"><< Back to Login</button></a>
</div>
</form>
<?php
if(isset($_POST['register']))
{
@$username=$_POST['username'];
@$password=$_POST['password'];
@$cpassword=$_POST['cpassword'];
if($password==$cpassword)
{
$query = "select * from user where username='$username'";
//echo $query;
$query_run = mysqli_query($connection,$query);
//echo mysql_num_rows($query_run);
if($query_run)
{
if(mysqli_num_rows($query_run)>0)
{
echo '<script type="text/javascript">alert("This Username Already exists.. Please try another username!")</script>';
}
else
{
$query = "insert into userinfotbl values('$username','$password')";
$query_run = mysqli_query($connection,$query);
if($query_run)
{
echo '<script type="text/javascript">alert("User Registered.. Welcome")</script>';
$_SESSION['username'] = $username;
$_SESSION['password'] = $password;
header( "Location: homepage.php");
}
else
{
echo '<p class="bg-danger msg-block">Registration Unsuccessful due to server error. Please try later</p>';
}
}
}
else
{
echo '<script type="text/javascript">alert("DB error")</script>';
}
}
else
{
echo '<script type="text/javascript">alert("Password and Confirm Password do not match")</script>';
}
}
else
{
}
?>
</div>
</body>
</html>