Question

我在google / youtube上遵循了很多教程，但是仍然无法使用php连接数据库。我完全按照有关数据库连接的文档进行了编码，但是没有用。我已经使用mysql仪表板创建了名为userregistration的数据库。这是myindex.html文件：

 <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>User Login and Registration</title>
<link rel="stylesheet" type="text/css" href="style.css">
<link rel="stylesheet" type="text/css"   href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
</head>
<body>
<div class="container">
    <div class="login-box">
    <div class="row">
        <div class="col-md-6 login-left">
            <h2>Login Here</h2>
            <form action="validation.php" method="post">
                <div class="form-group">
                    <label>Username</label>
                    <input type="text" name="user" class="form-control" required>
                </div>
                <div class="form-group">
                    <label>Password</label>
                    <input type="password" name="password" class="form-control" required>
                </div>
                <button type="submit" class="btn btn-primary">Login</button>

            </form>

        </div>
        <div class="col-md-6 login-right">
            <h2>Register Here</h2>
            <form action="registration.php" method="post">
                <div class="form-group">
                    <label>Username</label>
                    <input type="text" name="user" class="form-control" required>
                </div>
                <div class="form-group">
                    <label>Password</label>
                    <input type="password" name="password" class="form-control" required>
                </div>
                <button type="submit" class="btn btn-primary">Register</button>

            </form>

        </div>
    </div>
    </div>
</div>
</body>
</html>

这是我的Registration.php文件：

<?php

session_start();

$con = mysqli_connect('localhost','root','');
mysqli_select_db($con, 'userregistration');
$name = $_POST['user'];
$pass = $_POST['password'];

$s = "select * from  usertable where name='$name'";
$result = mysqli_query($con, $s);
$num = mysqli_num_rows($result);

if($num == 1){
    echo "Username Already Taken";
}else{
    $reg = "insert into usertable(name, password) values ('$name','$pass')";
    mysqli_query($con, $reg);
    echo "Registration Successful";
}
?>

我的代码有错误吗？

Answer 1

尝试直接使用具有数据库名称的连接

基于模式

$con = mysqli_connect("127.0.0.1", "my_user", "my_password", "my_db");

尝试

$con = mysqli_connect('localhost','root','','userregistration');

，并确保您的php页面位于正确的路径中
最终尝试添加正确的路径或至少添加相对路径

   <form action="./Registration.php" method="post">

Answer 2

您的PHP部分看起来还不错。也许您可以尝试通过添加这样的调试代码（如此处https://www.php.net/manual/en/function.mysqli-connect.php

中所示的调试代码）来查看PHP是否能够建立连接。

if (!$con) {
    echo "Error: Unable to connect to MySQL." . PHP_EOL;
    echo "Debugging errno: " . mysqli_connect_errno() . PHP_EOL;
    echo "Debugging error: " . mysqli_connect_error() . PHP_EOL;
    exit;
}

echo "Success: A proper connection to MySQL was made! The my_db database is great." . PHP_EOL;
echo "Host information: " . mysqli_get_host_info($con) . PHP_EOL;

最后，最重要的是，您可能不应该直接使用此功能，因为这可能会引入严重的SQL注入漏洞。 Google多介绍一些最佳做法。：）

如何使用PHP连接数据库MySql？

2 个答案: