designtopack/public/site/config/routes/upload-images.php

<?php

return [
  'pattern' => 'upload-images.json',
  'method' => 'POST',
  'action' => function () {

    throw new Exception(json_encode($_FILES), 1);
    
    $kirby = kirby();
    $request = $kirby->request();

    $files = $request->files();
    $data = $request->data();

    throw new Exception(json_encode([
        'files' => $files,
        'data' => $data,
    ]));
    
    $pageUri = $request->query()->get('pageUri');
    $page = page($pageUri);    
    
    if ($uploads = $request->files()) {

      $allFiles = $page->clientBriefImages()->toFiles()->pluck('uuid', ',');      
      
      $alerts  = [];
      throw new Exception(json_encode($uploads), 1);
      
      foreach ($uploads->get('images') as $upload) {
        // check for duplicate
        $files      = $page->files();
        $duplicates = $files->filter(function ($file) use ($upload) {
          // get original safename without prefix
          $pos              = strpos($file->filename(), '_');
          $originalSafename = substr($file->filename(), $pos + 1);

          return $originalSafename === F::safeName($upload['name']) &&
                  $file->mime() === $upload['type'] &&
                  $file->size() === $upload['size'];
        });

        if ($duplicates->count() > 0) {
          $duplicate = $duplicates->first();
          
          if (in_array($duplicate->uuid(), $allFiles)) {
            $allFiles[] = $duplicate->uuid();
            $alerts[$upload['name']] = "The file already exists, added to the field.";
          }
        }

        try {
          $name = crc32($upload['name'].microtime()). '_' . $upload['name'];
          $newFile = $page->createFile([
            'source'   => $upload['tmp_name'],
            'filename' => $name,
            'template' => 'image',
            'content' => [
                'date' => date('Y-m-d h:m')
            ]
          ]);

          $newFiles[] = $newFile;
          
          $success = 'Your file upload was successful';

          $allFiles[] = (string) $newFile->uuid();
        } catch (Exception $e) {
          $alerts[$upload['name']] = $e->getMessage();
        }
      }

      $newPage = $page->update([
        'clientBriefImages' => $allFiles
      ]);

      $images = [];

      foreach ($newPage->clientBriefImages()->toFiles() as $image) {
        $images[] = [
          'url' => $image->url(),
          'uuid' => (string) $image->uuid(),
          'tags' => $image->tags()->split(),
          'name' => $image->filename(),
          'description' => $image->description()->value(),
        ];
      }
      
      return compact('images', 'alerts');
    }

    return [
      'error' => 'Aucun fichier reçu.',
    ];
  }
];