我一直在制作登录/注册系统，我正在接近完成我的注册部分代码。我遇到的唯一问题是如何使用它，以便用户无法注册重复的用户名和电子邮件。我希望它能够工作，以便我的数据库不会接受这些信息，它会告诉用户有关错误的信息。任何帮助表示赞赏。
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<?php
session_start();
include 'loginlogoutregister.php';
//connecting to database
$link = mysqli_connect("localhost","root","","authentication");
if(isset($_POST['Login_Btn'])){
login($link);
}
if(isset($_POST['Register_Btn'])){
register($link);
}
if(isset($_POST['Logout_Btn'])){
logout($link);
}
?>
<html>
<head>
<Title>LogIn</Title>
<link rel="stylesheet" type="text/css" href="style.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
var modal = document.getElementById('PopUpLR');
var btn = document.getElementById("myBtn");
var span = document.getElementsByClassName("closeLR")[0];
btn.onclick = function() {
modal.style.display = "block";
}
span.onclick = function() {
modal.style.display = "none";
}
window.onclick = function(event) {
if (event.target == modal) {
modal.style.display = "none";
}
}
</script>
</head>
<body>
<div class = "headerContainer">
<div class = "headerLeft">
test
</div>
<div class="headerMiddle">
<h1>Website</h1>
<div><h4>
<?php
if(isset($_SESSION['username']) ){
echo "Welcome ".$_SESSION['username'];
}else{
echo "Logged Out ";
}
?>
</h4></div>
</div>
<div class = "headerRight">
<div class = "loginRegister">
<p>Login/Register</p>
</div>
</div>
</div>
<button id="myBtn">Open Modal</button>
<div id = "PopUpLR">
<div class = "PopUpLRContent">
<span class="closeLR">x</span>
<p>Some text in the Modal..</p>
</div>
</div>
</body>
</html>
#PopUpLR{
display: none; /* Hidden by default */
position: fixed; /* Stay in place */
z-index: 1; /* Sit on top */
left: 0;
top: 0;
width: 100%; /* Full width */
height: 100%; /* Full height */
overflow: auto; /* Enable scroll if needed */
background-color: rgb(0,0,0); /* Fallback color */
background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
}
.PopUpLRContent{
background-color: #fefefe;
margin: 15% auto; /* 15% from the top and centered */
padding: 20px;
border: 1px solid #888;
width: 80%; /* Could be more or less, depending on screen size */
}
.closeLR {
color: #aaa;
float: right;
font-size: 28px;
font-weight: bold;
}
.closeLR:hover,
.closeLR:focus {
color: black;
text-decoration: none;
cursor: pointer;
}
答案 0 :(得分：1)
在UNIQUE CONSTRAINT表格的email_user和username列上创建tb_user;如果您尝试插入重复项，则会抛出错误。
ALTER TABLE tb_user ADD CONSTRAINT constr1 UNIQUE (email_user);
答案 1 :(得分：-1)
您可以在$q = $op->save()之前使用帖子中的名称和密码组合进行SELECT查询。
如果它返回任何结果，则返回一条消息并阻止保存。