Extracting data through Wordpress database table - php

Question

I am trying to extract data from a Wordpress database so I can get it into a new database, but having a few issues figuring things out. This is just a small sample of how some of the Wordpress tables are like.
wp_posts
id | post_type | post_status |
----------------------------------
1 | portfolio | published | ... other data
wp_postmeta
id | post_id | meta_key | meta_value |
-----------------------------------------------------------------------
1 | 1 | item_submission_title | Some title | ... other data
2 | 1 | item_technology | a:1:{i:0;s:4:"2372";} |
3 | 1 | item_description | Some description |
wp_terms
id | term_id | name |
--------------------------------
1 | 2372 | Some name | ... other data
So essentially, I have to get all id's from wp_posts where post_type is portfolio and post_status is publish.
Using these id's I then need to get the meta_value for the 3 meta_key's shown in my wp_postmeta table.
The item_technology meta_value is serialized, so I need to then unserialize it. I then need to get its id (2372) and use this to obtain further data from the wp_terms table.
There is a lot more I need to do, but achieving the above will give me the understanding of how best to do this. I have a feeling I can somehow use joins here, but not sure.
At the moment, my attempt is very ineffecient and incomplete. This is what I currently have.
$conn = Database::getInstance();
$ids = getIDs($conn);
$dataArray = array();
foreach ($ids as $row) {
$data = getData($conn, $row['id']);
$dataArray[] = $data;
}
function getIDs($conn) {
$query = "SELECT `id` FROM `wp_posts` WHERE `post_type` = \"portfolio\" and `post_status` = \"publish\"";
$sql = $conn->dbc->prepare($query);
$sql->execute();
$row = $sql->fetchAll();
return $row;
}
function getData($conn, $id) {
$query = "SELECT `meta_value` FROM `wp_postmeta` WHERE `post_id` = $id AND `meta_key` = \"item_submission_title\"";
$sql = $conn->dbc->prepare($query);
$sql->execute();
$row = $sql->fetchAll();
return $row;
}
What would be the best way to achieve what I am after?
Thanks

Answer 1

Considering that you have a WordPress Database, I'll assume you also have a WordPress install attached to it. If not, you should, in order to make sure you get the data you want in the manner you want without having to recreate code that deals with the multitude of WP specific "idiosyncrasies".
So the first thing you'll do is "bootstrap" WordPress so you can obtain the DB connection and all of the WordPress functionality in one east step. So let's say you create a file in the WordPress root directory...
<?php
// This includes gives us all the WordPress functionality
require_once( dirname(__FILE__) . '/wp-load.php' );
// Set parameters to gather posts
$args = array(
'posts_per_page' => -1,
'offset' => 0,
'orderby' => 'date',
'order' => 'DESC',
'post_type' => 'portfolio',
'post_status' => 'publish',
'suppress_filters' => true
);
// Retrieve matching posts
$posts_array = get_posts( $args );
// Loop through posts to get Meta values
foreach ( $posts_array as $post )
{
$item_submission_title = get_post_meta( $post->ID, 'item_submission_title', true );
$item_technology = maybe_unserialize( get_post_meta( $post->ID, 'item_technology', true ) );
$item_description = get_post_meta( $post->ID, 'item_description', true );
// Do something with this information
...
}
Of course, you might now need to get it into the other DB. WordPress can also accommodate that with a simple and powerful interface...
$otherDB = new wpdb( 'username', 'password', 'database', 'localhost' );
$table = 'other_table';
$data = array(
'item_submission_title' => $item_submission_title,
'item_technology' => $item_technology,
'item_description' => $item_description,
);
$otherDB->insert( $table, $data );
More functions of the WPDB class can be found here: https://codex.wordpress.org/Class_Reference/wpdb