filter h1 tag to add a word at the beginning of the text

Question

I'm looking for the best way to obtain this.

For example, I have the h1 tag whic is: Web Design

I want to add, in all the h1 tags of a certain post type, the same word at the beginning, which is my keyword. So, the result would be: MYKEYWORD Web Design

I have clear that I have to use the_content filter. I have this code:

add_filter( 'the_content', 'handle_h1' );

function handle_h1( $content )
{
    //check if it's the post type which I look for
    if (  'MYPOSTTYPE' != get_post_type() )
        return $content;


    return str_ireplace( '<h1', '<a href="#">Back to the top</a><h1', $content );
}

The example above adds the a href tag before the h1 tags...

Which I want is to change the output text of the h1, as I mentioned above.

EXAMPLE:

Original:

<h1>Books</h1>

What I want

<h1>Our Books</h1>

So the word added is "Our".

Answer 1

This is my solution:

add_filter( 'the_title', 'change_title', 10, 2 );   
function change_title( $title, $postid ) {

    global $post;

    if( get_post_type() == MYPOSTTYPE && $title == $post->post_title ){            

        $title = "MYKEYWORD ".$title;            
    }

    return $title;
}