插入查询在php中不起作用，也不会抛出任何错误

Question

尝试在php中将用户插入我的用户表。插入查询似乎无法运行。我尝试手动添加电子邮件ID，它会检查重复的电子邮件ID，并且确实会出现错误，说明电子邮件ID存在，但由于某种原因，它不会插入到数据库中。有什么建议吗？`

<?php
$error = "";
if(array_key_exists("submit",$_POST )){


    $link = mysqli_connect ("localhost", "root","","secretdi");

    if (mysqli_connect_error()){
        die ("Connection to Database failed!");
    }

    print_r($_POST);

    if (!$_POST ['email']){
         $error .= "Email Address is required<br>";
    }
    if (!$_POST ['password']){
         $error .= "Password is required<br>";
    }
    if ($error != ""){
        $error = "<p>There were Error(s) in your form <p>".$error;
    }else {
        $query = "SELECT id FROM `users` WHERE `email` = '".mysqli_real_escape_string($link,$_POST['email'])."' LIMIT 1 ";


        $result = mysqli_query ($link, $query );

        if (mysqli_num_rows($result) > 0){
           $error = "That Email Address is already taken. Try to Log In ";

        }else {
            $query = "INSERT INTO `users` (`email`,`password`)VALUES ('".mysqli_real_escape_string($link, $_POST["email"])."','".mysqli_real_escape_string($link, $_POST["password"])."')";

        }
            if (!mysqli_query($link, $query )){
                $error = "Could Not Sign You Up! Please Try Again Later. ";
            } else{
                echo "Sign-Up Successfull.";
            }
        }
    }


?>

<div id = "error" > <?php echo $error; ?> </div>
<form method="post">
    <input type = "email" name = "email" placeholder = " Your Email">
    <input type = "password" name = "password" >
    <input type = "checkbox" name = "checkbox">
    <input type = "submit" name = "submit" value = "Sign - Up">
</form>`