Directory / File reader using generators

FileReader.php

<?php
class FileReader
{
  private $filenames;

  public function __construct($input)
  {
    if (is_file($input)) {
      $this->filenames = [ $input ];
    } elseif (is_dir($input)) {
      $this->filenames = new \DirectoryIterator($input);
    }elseif( $input instanceof \DirectoryIterator ){
      $this->filenames = $input;
    }elseif( is_array( $input )){
      $this->filenames = array_filter($input, function($value){
        return is_file( $value );
      });
    }
    
    if (empty($this->filenames)) {
      throw new NoFileSelectedException('The file or directory not exists');
    }
  }
  
  public function filenames()
  {
    foreach( $this->filenames as $file ){
      if( $file instanceof \DirectoryIterator ){
        if (!$file->isDot() && $file->isReadable()) {
          yield $file->getFilename();
        }
      }else{
        yield $file;
      }
    }
  }
  
  public function fp()
  {
    $fp = null;
    foreach($this->filenames() as $file ){
      $fp = fopen($file,'rb' );
      do{
        yield $fp;
      }while(!feof($fp));
      fclose($fp);
    }
  }
  
  public function by_entire()
  {
    foreach ($this->filenames() as $filename) {
      yield file_get_contents($filename);
    }
  }

  public function by_chunk($size = 10000)
  {
    foreach($this->fp() as $fp){
      yield fread( $fp, $size);
    }
  }
  
  public function by_line()
  {
    foreach($this->fp() as $fp ){
      yield trim( fgets($fp), "\n" );
    }
  }
}