Untitled

<!DOCTYPE html>
<head>
  <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">
  <meta charset="utf-8" />
  <title>Oleo Acme Redirect</title>
  <link rel="stylesheet" href="style.css">
  <link rel="shortcut icon" type="image/x-icon" href="favicon.ico" />
  <script src='https://www.google.com/recaptcha/api.js'></script>
</head>
<body>
  <h1>Oleo Acme Redirect</h1>
  <form>
    <input type="text" name="redirectUrl" placeholder="Redirect Link">
    <input type="submit" name="submit" value="Generate">
    <input type="checkbox" name="hide" value="true">Hide redirect destination<br  />
    <div class="g-recaptcha" data-sitekey="6LcLZ2wUAAAAAD5JPq-pu6ciRm7_j6bidwcVPuGA"></div>
  </form>
  <?php
  $conn = mysqli_connect("localhost", "----", "----", 'webDB');

  function IsInDb($key, $value){
    global $conn;
    $sql = "SELECT * FROM `redirects` WHERE binary `".$key."` = binary '".$value."';";
    $result = mysqli_query($conn, $sql);
    if(mysqli_num_rows($result) > 0) return true;
    return false;
  }

  function RandomString($length = 7){
    $char = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $charSize = strlen($char) - 1;
    while (true){
      $str = '';
      for($i = 0; $i != $length; $i++){
        $str = $str.$char[rand(0, $charSize)];
      }
      if(!IsInDb("shortUrl", $str)) break;
    }
    return $str;
  }

  if (isset($_GET['submit']))
  {
    global $conn;
    $url = $_GET['redirectUrl'];
    $hide = (isset($_GET['hide'])? '1' : '0');
    $url = filter_var($url, FILTER_SANITIZE_URL);

    if (filter_var($url, FILTER_VALIDATE_URL)) {
      $secretKey = "-----------------------";
      $responseKey = $_GET['g-recaptcha-response'];

      $capchaUrl = 'https://www.google.com/recaptcha/api/siteverify?secret='.$secretKey.'&response='.$responseKey;
      $response = file_get_contents($capchaUrl);
      $response = json_decode($response);
      if ($response->success){
        $short = '';
        if(IsInDb("redirectUrl", $url)){
          $sql = "SELECT `shortUrl` FROM `redirects` WHERE binary `redirectUrl` = binary '".$url."' LIMIT 1;";
          $result = mysqli_query($conn, $sql);
          if(mysqli_num_rows($result) > 0) {
            $short = mysqli_fetch_assoc($result)['shortUrl'];
          }
        }
        else{
          $short = RandomString();
          $sql = "INSERT INTO `redirects` (`redirectUrl`, `shortUrl`, `hide`) VALUES ('".$url."', '".$short."', '".$hide."');";
          $result = mysqli_query($conn, $sql);
        }
        $link = "https://oleo.acme.si/redirect/".$short;
        header("Location: ?short=".$short);
      }
      else{
        echo("<p>reCaptcha verification has failed. Try again.</p>");
      }
    } else {
      echo("<p>".$url." is not a valid URL.</p>");
    }
  }
  else if (isset($_GET['short'])){
    $short = $_GET['short'];
    if(IsInDb("shortUrl", $short)){
      $link = "https://oleo.acme.si/redirect/".$short;
      echo '<p>Generated a redirect url at <a href="'.$link.'">'.$link.'</a></p>';
    }
    else{
      echo "<p>This redirect link doesn't exist</p>";
    }
  }
  else {
    echo "<p>Enter a redirect link</p>";
  }
  ?>
  <br />
  <p>
    Go back <a href="http://oleo.acme.si">home</a>
  </p>
</body>