upload.php

<?php

print_r($_FILES);

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
  if (isset($_FILES['files'])) {
    $errors = [];
    $path = './trails/';
    $extensions = ['json','geojson'];

    $all_files = count($_FILES['files']['tmp_name']);

    for ($i = 0; $i < $all_files; $i++) {
      $file_name = $_FILES['files']['name'][$i];
      $file_tmp = $_FILES['files']['tmp_name'][$i];
      $file_type = $_FILES['files']['type'][$i];
      $file_size = $_FILES['files']['size'][$i];
      $exploded = explode('.', $_FILES['files']['name'][$i]);
      $file_ext = strtolower(end($exploded));
      
      $file = $path . $exploded[0] . '.json';

      if (!in_array($file_ext, $extensions)) {
        $errors[] = 'Extension not allowed: ' . $file_name . ' ' . $file_type;
      }
      
      if ($file_size > 2097152) {
          $errors[] = 'File size exceeds limit of 2MB: ' . $file_name . ' ' . $file_type;
      }

      if (empty($errors)) {
        move_uploaded_file($file_tmp, $file);
      }
    }
    if ($errors) print_r($errors);
  }
}