Need Help Understanding this PHP Code

Question

i am aware of the basics like what is a function, a class, a method etc. however i am totally confused on what exactly the below code does to read the image, i read it somewhere

Answer 1

class Image
{
  public $source = '';

    function __construct($filename)
    {
      $fp = fopen($filename, 'rb') or die("Image $filename doesn't exist");
      $buf = '';
      while(!feof($fp))
      {
        $buf .= fgets($fp, 4096);
      }
      $this->source = imagecreatefromstring($buf);
    }
}
$image = new Image('image.jpg');
/* use $image->source for image processing */
header('Content-Type: image/jpeg');
imagejpeg($image->source);