wp_update_post splitting my content

Hello, there,

I’m using this:

$my_post = array();
$my_post[‘ID’] = $page_id;
$my_post[‘post_content’] = file_get_contents(“archivo/last.html”);

print_r($my_post);
// Update the post into the database
echo wp_update_post( $my_post );

The file archivo/last.html is a long html file that is frecuently updated. But it just striped the contents of the file and it just update the page with a partial porcion of the file.

what can I do?