How to change meta data(title, description) for current post?

Question

I have a hook, that detects opening the post(publication):

add_action('the_post', 'post_callback');

function post_callback($post) {
   $post->post_title = "New title";
   $post->post_content = "New content";
}

It replaces post_title, $post->post_content data on the custom values.

How to change HTML meta data on the page(title, description) inside function: post_callback?

Answer 1

Try this:

New title

add_filter('wp_title', 'filter_posttitle');
function filter_posttitle($title) {
 $title = 'New title '.$title;
 return $title;
}

and new content add code in header.php

<?php if ( is_single() ) { ?>
    <meta name="description" content="" />
<?php } ?>

Answer 2

Try this:

add_filter('the_title', 'new_title', 10, 2);
function new_title($title, $id) {
    if('custom_version' == get_post_type($id))
        $title = 'New title '; 
    return $title;
}

and new content

add_filter( 'the_content', 'new_content' ); 
function new_content( $content ) { 
    if ( is_singular('post')) {
        $content = 'New content';
        }
    return $content;
}