MYSOPHAL/front/newsletter.php

<?php
require_once('../lib/tcpdf/templates/tcpdf_include.php');
include ('../model_controller/articles.list.php');

Session::checkLoginUser();

// --- Get Newsletter by ID ---
if (!isset($_GET['id']) || !is_numeric($_GET['id'])) {
    Html::redirect($CFG_GLPI["root_doc"] . "/front/newsletter.list.php");
    exit;
}

$newsletter_id = (int) $_GET['id'];

global $DB;
$stmt = $DB->prepare("SELECT * FROM glpi_newsletters WHERE id = ? AND archived = 0");
$stmt->bind_param("i", $newsletter_id);
$stmt->execute();
$result = $stmt->get_result();

if ($result->num_rows === 0) {
    Html::redirect($CFG_GLPI["root_doc"] . "/front/newsletter.list.php");
    exit;
}

$newsletter = $result->fetch_assoc();

// Path stored in DB
$path = $newsletter['path']; // e.g. "N1" or "N2" or folder name
$title = $newsletter['title'];

// ---------------------- Flipbook rendering ----------------------

echo "<h2 style='text-align:center;margin:20px 0;color:#27548A;'>".$title."</h2>";

$files = scandir('../file_upload/newsletter/'.$path);
$count = sizeof($files);

echo '<div class="book">';
$i = 2; // skip . and ..
while ($i < $count) {
    echo '
      <div class="page">
        <div class="front">
          <img src="'.$CFG_GLPI['root_doc'].'/file_upload/newsletter/'.$path.'/'.$files[$i].'" alt="Img '.($i).'">
        </div>';

    if ($count % 2 != 0 && $i+2 > $count) {
        echo '  
        <div class="back">
          <img src="'.$CFG_GLPI['root_doc'].'/file_upload/newsletter/'.$path.'/'.$files[2].'" alt="Img 2">
        </div>
      </div>';
    } else {
        echo '  
        <div class="back">
          <img src="'.$CFG_GLPI['root_doc'].'/file_upload/newsletter/'.$path.'/'.$files[$i+1].'" alt="Img '.($i+1).'">
        </div>
      </div>';
    }

    if ($count % 2 == 0 && $i+2 >= $count) {
        echo ' 
        <div class="page">
            <div class="front"></div> 
            <div class="back">
                <img src="'.$CFG_GLPI['root_doc'].'/file_upload/newsletter/'.$path.'/'.$files[2].'" alt="Img 2">
            </div>
        </div>';
    }
    $i += 2;
}
echo '</div>';
?>

<script>
const flipBook = (elBook) => {
  elBook.style.setProperty("--c", 0);
  elBook.querySelectorAll(".page").forEach((page, idx) => {
    page.style.setProperty("--i", idx);
    page.addEventListener("click", (evt) => {
      if (evt.target.closest("a")) return;
      const curr = evt.target.closest(".back") ? idx : idx + 1;
      elBook.style.setProperty("--c", curr);
    });
  });
};
document.querySelectorAll(".book").forEach(flipBook);
</script>

<style>
    * {
  box-sizing: border-box;
}

/* FlipBook */

body {
  /* or any other parent wrapper */
  margin: 0;
  display: flex;
  min-height: 100dvh;
  perspective: 1000px;
  font: 1em/1.4 "Poppins", sans-serif;
  overflow: hidden;
  color: hsl(180 68% 5%);
  background-image: radial-gradient(
    circle farthest-corner at 50% 50%,
    hsl(187 20% 88%) 30%,
    hsl(149 20% 94%) 100%
  );
}

.book {
  position: relative;
  display: flex;
  margin: auto;
  width: 65cqmin;
  /*1* let pointer event go trough pages of lower Z than .book */
  pointer-events: none;
  transform-style: preserve-3d;
  transition: translate 1s;
  translate: calc(min(var(--c), 1) * 50%) 0%;
  /* Incline on the X axis for pages preview */
  rotate: 1 0 0 20deg;
}

.page {
  /* PS: Don't go below thickness 0.5 or the pages might transpare */
  --thickness: 4;
  flex: none;
  display: flex;
  width: 100%;
  font-size: 2cqmin;
  /*1* allow pointer events on pages */
  pointer-events: all;
  user-select: none;
  transform-style: preserve-3d;
  transform-origin: left center;
  transition: transform 1s,
    rotate 1s ease-in
      calc((min(var(--i), var(--c)) - max(var(--i), var(--c))) * 50ms);
  translate: calc(var(--i) * -100%) 0px 0px;
  transform: translateZ(
    calc((var(--c) - var(--i) - 0.5) * calc(var(--thickness) * 0.23cqmin))
  );
  rotate: 0 1 0 calc(clamp(0, var(--c) - var(--i), 1) * -180deg);
}

.front,
.back {
  position: relative;
  flex: none;
  width: 100%;
  backface-visibility: hidden;
  overflow: hidden;
  background-color: #fff;
  /* Fix backface visibility Firefox: */
  translate: 0px;
}

.back {
  translate: -100% 0;
  rotate: 0 1 0 180deg;
}

/* That's it. Your FlipBook customization styles: */

.book {
  counter-reset: page -1;
  & a {
    color: inherit;
  }
}

.page {
  box-shadow: 0em 0.5em 1em -0.2em #00000020;
}

.front,
.back {
  display: flex;
  flex-flow: column wrap;
  justify-content: space-between;
  padding: 2em;
  border: 1px solid #0002;

  &:has(img) {
    padding: 0;
  }

  & img {
    width: 100%;
    height: 100%;
    object-fit: cover;
  }

  &::after {
    position: absolute;
    bottom: 1em;
    counter-increment: page;
    //content: counter(page) ".";
    font-size: 0.8em;
  }
}
.cover {
  &::after {
    content: "";
  }
}
.front {
  &::after {
    right: 1em;
  }
  background: linear-gradient(to left, #f7f7f7 80%, #eee 100%);
  border-radius: 0.1em 0.5em 0.5em 0.1em;
}
.back {
  &::after {
    left: 1em;
  }
  background-image: linear-gradient(to right, #f7f7f7 80%, #eee 100%);
  border-radius: 0.5em 0.1em 0.1em 0.5em;
}

.cover {
  background: radial-gradient(
      circle farthest-corner at 80% 20%,
      hsl(150 80% 20% / 0.3) 0%,
      hsl(170 60% 10% / 0.1) 100%
    ),
    hsl(231, 32%, 29%) url("https://picsum.photos/id/984/800/900") 50% / cover;
  color: hsl(200 30% 98%);
}

</style>