Try remove some things and use a suitable hook.
<?php // remove all spaces up of here too
/*
Plugin Name: RePhotosPic Plugin
Description: A plugin to retrieve photos and share them on the wordpress.
Version: 1.0
Author: Saeed pirdost
Copyright: 2012, Saeed pirdost
*/
// remove ?> <?php
add_filter('admin_notices', 'hello');
function hello()
{
echo 'Hello';
}
// remove ?>
UPDATE:
Remove myprint();
place it inside a WP hook too. Like this:
add_filter('admin_notices', 'myprint');
function myprint()
{
echo "hello";
}