Drupal 9 - Working with files

file_func.php

<?php

use Drupal\file\Entity\File;

// Load a file using its ID
  $file = File::load($fid);


// Find a file using its URI

  /** @var \Drupal\file\FileInterface[] $files */
  $files = \Drupal::entityTypeManager()
    ->getStorage('file')
    ->loadByProperties(['uri' => $found_file_url]);

  /** @var \Drupal\file\FileInterface|null $found_file_url */
  $image = reset($files) ?: NULL;


// Get file details

  $uri = $file->getFileUri();          // public://{location}/{file name}.{extension}
  echo 'File name: ' . $file->getFilename . ', type:' . $file->getMimeType . ', size: ' . $file->getSize . ', Permanent:' . $file->isPermanent . ', Temporary:' . $file->isTemporary;


// Create a managed file.

  /** @var \Drupal\Core\File\FileSystemInterface $filesystem */
  $filesystem = \Drupal::service('file_system');
  // Create file entity.
  $image = File::create();
  $image->setFileUri($file_url);
  $image->setOwnerId(\Drupal::currentUser()->id());
  $image->setMimeType('image/' . pathinfo($file_url, PATHINFO_EXTENSION));
  $image->setFileName($filesystem->basename($file_url));
  $image->setPermanent();
  $image->alt = 'Product image';
  $image->title = 'Product image';
  $image->save();

// Assign the file to a file/image field
  $variation->field_product_image = $image;
  $variation->save();


// Getting data from a file/image field    
  $image_field = $variation->field_product_image;
  $tid = $existing_file_ref->target_id;
  $alt = $existing_file_ref->alt;
  $title = $existing_file_ref->title;
  $width = $existing_file_ref->width;
  $height = $existing_file_ref->height;

   if (isset($tid)) {
     // Load a file using its ID.
     $file = File::load($tid);
     $file_url = $file->getFileUri();
   }

file_system.php

<?php

// Build a URI
$directory = file_build_uri("folder");    // public://folder
$file = file_build_uri("folder/file.ext");    // public://folder/file.ext


// Use the file_system service to find jpg files in $directory
/** @var \Drupal\Core\File\FileSystemInterface $file_system */
$file_system = \Drupal::service('file_system');
$files = $file_system->scanDirectory($directory, '/.*\.jpg$/');

// get info about the files found
foreach($files as $file) {
  $file_name_no_ext = $file->name;
  $file_name_with_ext   = $file->filename;
  $file_uri = $file->uri;
}

media_func.php

<?php

  // Create media entity holding a reference to a managed file (like the one created in file_func.php).
   /** @var \Drupal\media\MediaInterface $media */
  $image_media = Media::create([
    'bundle' => 'image',
    'uid' => \Drupal::currentUser()->id(),
    'langcode' => \Drupal::languageManager()->getDefaultLanguage()->getId(),
    'status' => Media::PUBLISHED,
    'field_image' => [
      'target_id' => $image->id(),
      'alt' => t('Image for product '),
      'title' => t('Image for product'),
    ],
  ]);
  $image_media->save();

write_and_load_data.php

<?php

use Drupal\Core\File\FileSystemInterface;

class LoadAndSaveDataExample {
 
  const FILE_SCHEME = 'private://';

  const DATA_CACHE_FOLDER = 'bank_of_england';

  const DATA_CACHE_FILENAME = 'mydata.xml';
  
  private function loadData() {
    $directory = self::FILE_SCHEME . '/' . self::DATA_CACHE_FOLDER;
    $file_path = $directory . '/' . self::DATA_CACHE_FILENAME;
    return file_get_contents($file_path);
  }

  private function writeData($data) {
    // Make sure folder exists
    $directory = self::FILE_SCHEME . '/' . self::DATA_CACHE_FOLDER;
    /** @var \Drupal\Core\File\FileSystemInterface $file_system */
    $file_system = \Drupal::service('file_system');
    $file_system->prepareDirectory($directory, FileSystemInterface::CREATE_DIRECTORY | FileSystemInterface::MODIFY_PERMISSIONS);

    // Write the data
    $file_path = $directory . '/' . self::DATA_CACHE_FILENAME;
    /** @var \Drupal\file\FileRepositoryInterface $fileRepository */
    $fileRepository = \Drupal::service('file.repository');
    $fileRepository->writeData($data, $file_path, FileSystemInterface::EXISTS_REPLACE);
  }  

}

z_file_system.php

<?php

// Check if a file exists.

  $destination = '/folder/my_file.pdf';

  // PHP code
    if (!file_exists($destination)) {
    }

  // Drupal code
    /** @var \Drupal\Core\File\FileSystemInterface $file_system */
    $file_system = \Drupal::service('file_system');
    if ($file_system->getDestinationFilename($destination, \Drupal\Core\File\FileSystemInterface::EXISTS_ERROR)) {

    }

z_media_func.php

<?php

use Drupal\media\Entity\Media;

// Load by ID
$media = Media::load($media_id);
// Load by ID - with no use section.
$media = \Drupal\media\Entity\Media::load($media_id);

// Util functions

  private function get_media_url_from_mid($media_id) {
    $url = NULL;
    $media = \Drupal\media\Entity\Media::load($media_id);
    if (isset($media)) {
      $fid = $media->getSource()->getSourceFieldValue($media);
      $file = \Drupal\file\Entity\File::load($fid);
      $uri = $file->getFileUri();
      $url = \Drupal::service('file_url_generator')->generateString($uri);
    }
    return $url;
  }

  private function render_media($media_id) {
    $media = \Drupal\media\Entity\Media::load($mid);
    if (!empty($media)) {
      $builder =  \Drupal::entityTypeManager()->getViewBuilder('media');
      $rendered_media = $builder->view($media, 'default');
    }
    return $rendered_media ?? NULL;    
  }