Set order of uploaded images (JS, PHP)

My goal is to get a way to upload multiple images and also set in which order they should be displayed later on (it’s for an ecommerce website). I have an idea which seems to work. But I would like to know if there is a better way of doing this. Here is my code. Let’s assume the number of images is limited to 3.

1. One input for multiple images.
2. Preview images and make them sortable.
3. Store the order in hidden inputs.
4. Store the images in the filesystem.
5. Add the path and order index of every image to the database.

HTML

<!-- One input for all images -->
<input type="file" name="images[]" onchange="previewImages(this)" multiple>

<!-- This <div> will be made sortable with SortableJS -->
<div id="preview-parent">
  <div class="preview">
    <!--
    Hidden input to save the order of images.
    The idea is to have images_order[name_of_image] = index.
    name_of_image and index will be set with JavaScript
    -->
    <input class="order-input" type="hidden" name="images_order[]" value="0">
    <!-- <img> is for preview -->
    <img class="preview-image" src="" alt="Image1">
  </div>
  <div class="preview">
    <input class="order-input" type="hidden" name="images_order[]" value="1">
    <img class="preview-image" src="" alt="Image2">
  </div>
  <div class="preview">
    <input class="order-input" type="hidden" name="images_order[]" value="2">
    <img class="preview-image" src="" alt="Image3">
  </div>
</div>

JavaScript

function previewImages(input) {

    // First I take the images
    var file = input.files

    // Then I go through each of them. This code is based on the explanation
    // from https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsDataURL
    for (var i = 0; i < file.length; i++) {
        let preview = document.querySelectorAll('.preview-image')[i]
        let reader  = new FileReader()

        reader.onloadend = function () {
            preview.src = reader.result
        }

        if (file[i]) {
            reader.readAsDataURL(file[i])

            // In addition to previewing images I take their names
            // and put them into my hidden inputs
            let order_inputs = document.querySelectorAll('.order-input')
            order_inputs[i].name = 'images_order[' + file[i].name +']'
        } else {
            preview.src = ""
        }
    }
}

// I make the images sortable by means of SortableJS
var el = document.getElementById('preview-parent')
new Sortable(el, {
    animation: 150,

    // This function updates the values of my hidden inputs
    // every time a change is made
    onEnd: function (event) {
        let order_inputs = document.querySelectorAll('.order-input')
        for (var i = 0; i < order_inputs.length; i++) {
            order_inputs[i].value = [i]
        }
    }
})

function previewImages(input) {
    var file = input.files

    for (var i = 0; i < file.length; i++) {
        let preview = document.querySelectorAll('.preview-image')[i]
        let reader  = new FileReader()

        reader.onloadend = function () {
        preview.src = reader.result
        }

        if (file[i]) {
            reader.readAsDataURL(file[i])
            let order_inputs = document.querySelectorAll('.order-input')
            order_inputs[i].name = 'images_order[' + file[i].name +']'
        } else {
          preview.src = ""
        }
    }
}

var el = document.getElementById('preview-parent')
new Sortable(el, {
    animation: 150,
    onEnd: function (event) {
        let order_inputs = document.querySelectorAll('.order-input')
        for (var i = 0; i < order_inputs.length; i++) {
        order_inputs[i].value = [i]
        }
    }
})

#preview-parent {
  display: flex;
  gap: 1rem;
  margin: 1rem;
}
.preview {
  height: 100px;
  width: 100px;
  padding: 1rem;
  border: 1px solid grey;
}
.preview img {
  max-height: 100%;
  max-width: 100%;
}

<script src="https://cdn.jsdelivr.net/npm/sortablejs@latest/Sortable.min.js"></script>

<input type="file" name="images[]" onchange="previewImages(this)" multiple>

<div id="preview-parent">
  <div class="preview">
    <input class="order-input" type="hidden" name="images_order[]" value="0">
    <img class="preview-image" src="" alt="Image1">
  </div>
  <div class="preview">
    <input class="order-input" type="hidden" name="images_order[]" value="1">
    <img class="preview-image" src="" alt="Image2">
  </div>
  <div class="preview">
    <input class="order-input" type="hidden" name="images_order[]" value="2">
    <img class="preview-image" src="" alt="Image3">
  </div>
</div>

I haven’t figured out yet how to limit the number of submitted images. But I saw a number of discussions about that, so I hope it will not be a problem.

PHP. The next step is done by means of PHP (CodeIgniter 4). I take the images, store them in my filesystem. Also I add the path to every image and its order index (taken from the hidden input) to the database. Later when a user will open certain product, the data will be taken from the database and ordered by order index. So basically my controller has this:

// I inserted the product before and can get its id
$product_id = $this->products->insertID();
// This line is just for reference, I actually create $input earlier
$input = $this->request->getPost();

// Here I take all the images as suggested in CodeIgniter docs
if($imagefile = $this->request->getFiles())
{
    foreach($imagefile['images'] as $img)
    {
        if ($img->isValid() && ! $img->hasMoved())
        {
            // Store each image
            $name = $img->getName();
            $img->move('assets/images/'.$product_id, $name);

            // Add info about the image to the database
            $data = [
                'product_id'    => $product_id,
                'path'          => base_url('assets/images/'.$product_id.'/'.$name),
                'order_index'   => $input['images_order'][$name],
            ];
            
            $this->imagesModel->insert($data);
        }
    }
}

It would be perfect if I could upload multiple images at once and then not only reorder them but also be able to replace one of the images. If someone could share any ideas, I will appreciate it very much!

Answer

After long time I have returned to this project and made further research. So I would like to share my solution.

So I have decided that a convenient option will be to have only one input for multiple images. The user clicks it and chooses the needed images. If he needs to add more images after this, he clicks the same input again and the new images are added to the list. All images immediately appear as previews with the “delete” button. So if the user needs to replace one image, he can delete it, upload a new image and move it to the needed place.

The PHP code from my post does not require any changes. The work is done in Javascript. There are lots of lines of code, but a big part of them is simply for dynamic generating of previews. Please see the snippet.

// DataTransfer allows updating files in input
var dataTransfer = new DataTransfer()

const form = document.querySelector('#form')
const input = document.querySelector('#input')

input.addEventListener('change', () => {

  let files = input.files

  for (let i = 0; i < files.length; i++) {
    // A new upload must not replace images but be added
    dataTransfer.items.add(files[i])

    // Generate previews using FileReader
    let reader, preview, previewImage
    reader = new FileReader()

    preview = document.createElement('div')
    previewImage = document.createElement('img')
    deleteButton = document.createElement('button')
    orderInput = document.createElement('input')

    preview.classList.add('preview')
    document.querySelector('#preview-parent').appendChild(preview)
    deleteButton.setAttribute('data-index', i)
    deleteButton.setAttribute('onclick', 'deleteImage(this)')
    deleteButton.innerText = 'Delete'
    orderInput.type = 'hidden'
    orderInput.name = 'images_order[' + files[i].name + ']'

    preview.appendChild(previewImage)
    preview.appendChild(deleteButton)
    preview.appendChild(orderInput)

    reader.readAsDataURL(files[i])
    reader.onloadend = () => {
      previewImage.src = reader.result
    }
  }

  // Update order values for all images
  updateOrder()
  // Finally update input files that will be sumbitted
  input.files = dataTransfer.files
})

const updateOrder = () => {
  let orderInputs = document.querySelectorAll('input[name^="images_order"]')
  let deleteButtons = document.querySelectorAll('button[data-index]')
  for (let i = 0; i < orderInputs.length; i++) {
    orderInputs[i].value = [i]
    deleteButtons[i].dataset.index = [i]
    
    // Just to show that order is always correct I add index here
    deleteButtons[i].innerText = 'Delete (index ' + i + ')'
  }
}

const deleteImage = (item) => {
  // Remove image from DataTransfer and update input
  dataTransfer.items.remove(item.dataset.index)
  input.files = dataTransfer.files
  // Delete element from DOM and update order
  item.parentNode.remove()
  updateOrder()
}

// I make the images sortable by means of SortableJS
const el = document.getElementById('preview-parent')
new Sortable(el, {
  animation: 150,

  // Update order values every time a change is made
  onEnd: (event) => {
    updateOrder()
  }
})

#preview-parent {
  display: flex;
}
.preview {
  display: flex;
  flex-direction: column;
  margin: 1rem;
}
img {
  width: 100px;
  height: 100px;
  object-fit: cover;
}

<script src="https://cdn.jsdelivr.net/npm/sortablejs@latest/Sortable.min.js"></script>
<form method="post" enctype="multipart/form-data" id="form">
    <input type="file" name="images[]" id="input" multiple>
    <button type="submit">Save</button>
</form>

<!-- This <div> will be made sortable with SortableJS -->
<div id="preview-parent">
  <!-- After upload Javascript will generate previews with this pattern
  <div class="preview">
    <img src="...">
    <button data-index=0>Delete</button>
    <input type="hidden" name="images_order['name']" value=0>
  </div>
  -->
</div>