WordPress migration template

migration.php

<?php

// we need memory and time

ini set( 'memory limit', -1);
set_time_limit( 0 );

// WordPress environment

include( 'wp-load.php' );

// database to import posts from

global $wpdb;
$external_db = new wpdb( IMPORT_USER, IMPORT_PASS, IMPORT_DB, IMPORT_SERVER );

foreach ( $external_db->get_results("<POSTS QUERY HERE>") as $p ) {

    // insert a post

    $args = array(
        'post_title' => $p->title_column,
        'post_content' => $p->content_column,
        /* other database fields that match posts's columns */
    );
    $post_id = wp_insert_post( $args );

    // parsing the post content for images

    $content = $p->content_column;
    $doc = new DOMDocument();
    @$doc->loadHTML($content);
    $tags = $doc->getElementsByTagName('img');

    // import images as attachments

    foreach ($tags as $tag) {

        $url = echo $tag->getAttribute('src');
        $image_id = media_sideload_image($url, $post_id);

        // update post URLs

        $image_url = wp_get_attachment_image_src($image_id);
        $content = str_replace($url, $image_url, $content);

    }

    // update post content

    $args['ID'] = $post_id;
    $args['post_content'] = $content;
    wp_update_post($args);

}