Replace small links inside the content Wordpress with the permalink

fix_content_links.php

<?php

function fix_links_content($content)
{
    if (is_single() && get_post_type() === 'post') {
        $content = preg_replace_callback('(\/\?p=[0-9]*)',
            'replace_query_string_url', $content);
    }

    return $content;
}

function replace_query_string_url($matches)
{
    $id = explode('=', $matches[0])[1];

    return get_permalink($id);
}

add_filter('the_content', 'fix_links_content');