use Cake\Filesystem\Folder;

$dir = new Folder('/path/to/folder');
$files = $dir->find('.*\.php');

foreach ($files as $file) {
    $file = new File($dir->pwd() . DIRECTORY_SEPARATOR . $file);
    $contents = $file->read();
    // $file->write('I am overwriting the contents of this file');
    // $file->append('I am adding to the bottom of this file.');
    // $file->delete(); // I am deleting this file
    $file->close(); // Be sure to close the file when you're done
}