php - 错误太多重定向

Question

尝试创建我的 server.php 脚本，所以直到现在一切都很好。我想防止重新提交表单，并将 header('location: index.php'); 添加到我的脚本中。然后我遇到了问题:ERR_TOO_MANY_REDIRECTS。正如你们中的许多人已经了解的那样，我的数据库中充满了垃圾。所以，这是我的代码:

<?php

$username = $email = $password = "";
$usernameErr = $emailErr = $passwordErr = "";
$servername = 'localhost';
$serveruser = 'root';
$serverpassword = 'root';
$db = 'example';

$conn = new mysqli($servername, $serveruser, $serverpassword, $db);

if($conn->connect_error){
    die("Connection failed: " . $conn->connect_error);
}

if(isset($_POST['register'])) {
    $username = mysqli_real_escape_string($conn,$_POST['username']);
    $email = mysqli_real_escape_string($conn,$_POST['email']);
    $password = mysqli_real_escape_string($conn,$_POST['password']);

    if(empty($username)) {
        $usernameErr = "Username is required";
    } else {
    $username = test_input($_POST["username"]);

    if(!preg_match("/^[a-zA-z ]*$/", $username)){
        $usernameErr = "Only letters and whitespaces allowed";
    }

    }

    if(empty($email)) {
        $emailErr = "Email is required";
    } else {
    $email = test_input($_POST["email"]);

    if(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $emailErr = "Wrong email format";
    }

    }

    if(empty($password)) {
        $passwordErr = "Password required";
    } else {
    $password = test_input($_POST["password"]);
        }
}

if ($usernameErr == "" && $emailErr == "" && $passwordErr == "") {
    $sql = "INSERT INTO users (username, email, password)
    VALUES('$username','$email','$password')";

    if($conn->query($sql) === TRUE) {
    } else {
        echo "Error: " . $sql . "<br>" . $conn->error;
    }

    header("location: index.php"); 
}

function test_input($data) {
    $data = trim($data);
    $data = htmlspecialchars($data);
    $data = stripslashes($data);
    return $data;
}

?>

Answer 1

为了防止TOO MANY REDIRECT 放置这段代码

if ($usernameErr == "" && $emailErr == "" && $passwordErr == "") {
$sql = "INSERT INTO users (username, email, password)
VALUES('$username','$email','$password')";

if($conn->query($sql) === TRUE) {
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

header("location: index.php"); 

在

if(isset($_POST['register'])) { //.................}

检查错误后的这个 block

并且为了防止重新提交表单，请使用此问题的已接受答案

Preventing form resubmission