gistfile1.phtml

$Email = new CakeEmail('default');                       // Php file
            $Email->template('default', 'default')                   
                    ->to($user_email)
                    ->attachments(array(
                                        'photo.png' => array(
                                        'file' => 'http://135smart.com/wp-content/uploads/2014/08/logo.png',
                                        'mimetype' => 'image/png',
                                        'contentId' => 'cid:b7f792ab-98b1-435c-bbdb-14610be008c9'
                                                       )
                                ))
                    ->subject('Your Daily Tasks')
                    ->send($email_body);
                
            }


<img src="cid:b7f792ab-98b1-435c-bbdb-14610be008c9">   // layout File

   $Email->attachments(array(
        'logo.png' => array(
            'file' => '/absolute/path/to/file.png',
            'mimetype' => 'image/png',
            'contentId' => 'b7f792ab-98b1-435c-bbdb-14610be008c9'
        )
    ));