how to place a link on the first post only using a plugin

Question

i want to add a link to the first post of every WP blog that i have. For example this simple function adds the link to every post.

    function add_link($link){

    $link .= '<a href="http://site.com">Link</a>';
return $link;
    }
    add_filter('the_content','add_link');

so basically instead of the link showing below each post, I want it to show only at the bottom of the first post only.

thanks.

Answer 1

Trivial with some basic logic

Add before your function:

$added = false;

Then check e.g.:

    if(!$added ){
        $added = true;
        $link .= '<a href="http://site.com">Link</a>';
    }

Answer 2

Just remove the filter when it is called the first time:

function add_link($link)
{
    // this will guarantee the filter will not be called again.
    remove_filter( current_filter(), __FUNCTION__ );
    return $link . '<a href="http://site.com">Link</a>';
}