wordpress missing P tag - wordpress

Question

I am creating a file outside of wordpress but i want to get wordpress post etc. I created the following which does whar i want it to do but it is missing th P tags. if i view this post through wp-admin it looks fine. if i view it through this function it doe snot look find
ini_set('display_errors','on');
//Global WordPress
global $wpdb;
if(!isset($wpdb))
{
require_once('wp-config.php');
require_once('wp-load.php');
require_once('wp-includes/wp-db.php');
}
$args = array("post_title" => $_GET['name'],"category_name"=>"knowledge-map");
$query = get_posts( $args );
$posttitle = $_GET['name'];
$postid = $wpdb->get_var( "SELECT ID FROM $wpdb->posts WHERE post_title = '" . $posttitle . "'" );
$post = $getpost= get_post($postid);
$post_title = sanitize_post_field( 'post_title', $post->post_title, $post->ID, 'display' );
$post_content = sanitize_post_field( 'post_content', $post->post_content, $post->ID, 'display' );
//$postcontent= $getpost->post_content;
//setup_postdata( $getpost );
$data = $post->post_content;
//foreach ( $getpost as $post ) : setup_postdata( $post );
//$data = get_the_title() . the_content();
//endforeach;
wp_reset_postdata();
echo $data;

Answer 1

post_content won't show proper formatting...basically ever. You need to apply the_content filter to it:
echo apply_filters('the_content', $data);
Here's where it's mentioned in the Codex.
While wpautop will only add paragraph tags where new lines exist, the_content runs a bunch of core filters (including wpautop). From the source, the_content includes:
add_filter( 'the_content', 'wptexturize' );
add_filter( 'the_content', 'convert_smilies' );
add_filter( 'the_content', 'convert_chars' );
add_filter( 'the_content', 'wpautop' );
add_filter( 'the_content', 'shortcode_unautop' );
add_filter( 'the_content', 'prepend_attachment' );

Answer 2

you can also use wpauto, it uses in wordpress for auto formatting of text
echo wpautop( $post_content );

Answer 3

Not very techy, but I found that if I copy everything from the "text" area in a Wordpress post, then paste it into a markdown to HTML editor, then it results in tags being added wherever Wordpress omits them!
Copy the "Text" from a Wordpress post
Paste into markdown/HTML editor
View the HTML for that markdown