Hacky way to import pictures after a WordPress site migration that didn't go well.

foo.php

// This will search through all blog content and find/replace <a href> and <img src> links 
// It will find images on the old multi-site host, e.g. http://dtbaker.net/wp-content/uploads/sites/* and import those images into the new blog, then update the links/src in the post content.

add_action('init', function(){

    if(isset($_REQUEST['do_import'])){
        ini_set('display_errors',true);
        ini_set('error_reporting',E_ALL);
        require_once ('wp-admin/includes/admin.php');
        $posts = get_posts(array(
                'posts_per_page' => '-1'
        ));
        foreach($posts as $post){

            $post = (array)$post;

            $content = $post['post_content'];

            $content = str_replace('https://new.dtbaker.net/wp-content', 'https://dtbaker.net/wp-content', $content);
            $content = str_replace('http://new.dtbaker.net/wp-content', 'https://dtbaker.net/wp-content', $content);

            if( preg_match_all('#<a.*href="(https?://dtbaker\.net/wp-content/uploads/sites/[^"]+)"[^>]*>#imsU', $content, $matches)){

                print_r($matches);

                foreach($matches[1] as $key => $url){
                    $url = str_replace('dtbaker.net','old.dtbaker.net',$url);

                    echo "Importing $url ";
                    $imported_url = media_sideload_image($url, $post['ID'], basename($url), 'src');
                    if($imported_url){
                        echo " ... as $imported_url <br>\n";
                        $new_image_tag = str_replace( $matches[1][$key], $imported_url, $matches[0][$key] );
                        echo "New tag is: $new_image_tag \n";
                        $content = str_replace($matches[0][$key], $new_image_tag, $content);
                    }else{
                        echo "FAILED TO IMPORT";
                    }

                }

            }

            if( preg_match_all('#<img.*src="(https?://themes\.dtbaker\.net/wp-content/uploads/sites/[^"]+)"[^>]*>#imsU', $content, $matches)){

                print_r($matches);

                foreach($matches[1] as $key => $url){
                    $url = str_replace('themes.dtbaker','old.dtbaker',$url);

                    echo "Importing $url ";
                    $imported_url = media_sideload_image($url, $post['ID'], basename($url), 'src');
                    if($imported_url){
                        echo " ... as $imported_url <br>\n";
                        $new_image_tag = str_replace( $matches[1][$key], $imported_url, $matches[0][$key] );
                        echo "New tag is: $new_image_tag \n";
                        $content = str_replace($matches[0][$key], $new_image_tag, $content);
                    }else{
                        echo "FAILED TO IMPORT";
                    }

                }

            }
            if( preg_match_all('#<img.*src="(https?://dtbaker\.net/wp-content/uploads/sites/[^"]+)"[^>]*>#imsU', $content, $matches)){

                print_r($matches);

                foreach($matches[1] as $key => $url){
                    $url = str_replace('dtbaker.net','old.dtbaker.net',$url);

                    echo "Importing $url ";
                    $imported_url = media_sideload_image($url, $post['ID'], basename($url), 'src');
                    if($imported_url){
                        echo " ... as $imported_url <br>\n";
                        $new_image_tag = str_replace( $matches[1][$key], $imported_url, $matches[0][$key] );
                        echo "New tag is: $new_image_tag \n";
                        $content = str_replace($matches[0][$key], $new_image_tag, $content);
                    }else{
                        echo "FAILED TO IMPORT";
                    }

                }

            }

            if($content && $content != $post['post_content']){
                echo $post['ID']. " ";
                $my_post = array(
                    'ID'           => $post['ID'],
                    'post_content' => $content,
                );
                wp_update_post($my_post);
            }
        }

        echo 'done';
        exit;
    }

});