Wordpress ob_start / output buffering

<?php

/*
::_di_frontend.php::
// How to replace template variables with PHP variables
function get_replacement_vars(){

    return array(
        '{post_id}' => get_the_ID(),
        '{post_title}' => get_the_title()
    );

}

$replacements = get_replacement_vars();
$output = str_replace(array_keys($replacements),array_values($replacements), $output);
*/

function buffer_callback($buffer){
    // manipulate HTML (replace template tags,
    return str_replace("{name}", "Chris", $buffer);
}

function ob_init(){
    ob_start('buffer_callback');
}
add_action('template_redirect', 'ob_init', 0);

function ob_shutdown(){
    ob_end_flush();
}
add_action('shutdown', 'ob_shutdown', 1000);

?>