Some files returning Error 520
<p>Some of my files in my web server is returning <code>Error 520: Web server is returning an unknown error</code>. As far as I know, the files returning the errors are <code>index.php</code> and <code>google0f3d9b***.html</code> (used to verify Google Webmaster Console).</p>

<p>Below is my <code>.htaccess</code> file:</p>

<pre><code>RewriteBase /

# Force non-www version
RewriteCond %{HTTP_HOST} ^www\.yikjin\.ga [NC]
RewriteRule ^(.*)$ https://yikjin.ga/$1 [L,R=301]

# Prevent 000webhost ads from poping up
php_value auto_append_file none

# Prevent directory listing
Options -Indexes

# Make index.php default
DirectoryIndex index.php
</code></pre>

<p>and my <code>index.php</code>:</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
    &lt;!-- ... --&gt;
&lt;/head&gt;

&lt;body&gt;
&lt;header&gt;
    &lt;img src="/drawable/images/me.jpg" width="6%" alt="That's us!" title="That's us!"&gt;
    &lt;span&gt;Welcome to Cards!&lt;/span&gt;
&lt;/header&gt;

&lt;div id="login"&gt;
    &lt;img src="/drawable/images/cards.jpg" alt width="40%" height="auto"&gt;
    &lt;h2 id="welcome"&gt;Welcome back,&lt;br/&gt;
        &lt;span id="user"&gt;user&lt;/span&gt;
    &lt;/h2&gt;
    &lt;h4&gt;Please re-enter your password&lt;/h4&gt;
    &lt;form method="post"&gt;
        &lt;label for="userid"&gt;Username&lt;/label&gt;
        &lt;br/&gt;
        &lt;input type="text" title="What's your username?
   eg. johntan" id="userid" name="userid" required&gt;
        &lt;br/&gt;
        &lt;span id="user-err"&gt;&lt;/span&gt;
        &lt;br/&gt;
        &lt;label for="pass"&gt;Password&lt;/label&gt;
        &lt;br/&gt;
        &lt;input type="password" title="What's your password?
   eg. *****" id="pass" name="pass" required&gt;
        &lt;br/&gt;
        &lt;span id="pass-err"&gt;&lt;/span&gt;
        &lt;br/&gt;
        &lt;input type="button" value="&amp;lsaquo; Back" onclick="javascript:window.history.back();"&gt;
        &lt;input type="submit" value="Continue &amp;rsaquo;" name="login"&gt;
        &lt;a href="#" target="_blank"&gt;Not you?&lt;/a&gt;
    &lt;/form&gt;
    &lt;br/&gt;
    &lt;a href="/register.php"&gt;Register now&lt;/a&gt;
&lt;/div&gt;

    &lt;link href="/drawable/css/design.css" type="text/css" rel="stylesheet"&gt;
    &lt;link href="https://fonts.googleapis.com/css?family=Open+Sans:300" type="text/css" rel="stylesheet"&gt;

&lt;!-- Begin Cookie Consent --&gt;
&lt;script type="text/javascript"&gt;
    window.cookieconsent_options = {"message":"We love cookies. So we use them. :D","dismiss":"Got it!","learnMore":"Whyyy...","link":null,"theme":"dark-bottom"};
&lt;/script&gt;
&lt;script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/cookieconsent2/1.0.9/cookieconsent.min.js"&gt;&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;

&lt;?php
    include("/drawable/connect.php"); /* $dbcon is from this file */

    if (isset($_POST['login'])) {
        $userid = $_POST['userid'];
        $pass = $_POST['pass'];

        $check_user = "SELECT * FROM login WHERE userid = '$userid' AND password = '$pass'";
        $user_query = mysqli_query($dbcon, $check_user);

        if (mysqli_num_rows($user_query)) {
            $_SESSION['user'] = $userid;
            header("Location: welcome.php");
        }
        else {
            echo "&lt;script&gt;alert('Invalid credentials supplied; please retry');&lt;/script&gt;";
        }
    }
?&gt;
</code></pre>

<p>I think it is a problem with my <code>.htaccess</code> file but I can't seem to figure out what. I am using 000webhost as my web server and Cloudflare. The link to my site is <a href="http://yikjin.ga/" rel="nofollow">yikjin.ga</a>. May I know what is causing the website not to work? Thanks in advance!</p>