Yesterday a friend emailed me asking for help. Her old WP installation had become corrupt – through a bad plugin or something – and she couldn’t bring it back to life. So she decided to start fresh, with a new WP installation on a new server. She wanted to know if it was possible to salvage her old posts, which (as she could see in PHPMyAdmin) were still in the old database. Here’s a copy of the email I wrote to her, on the off chance that it helps someone else.

Note that this technique should be used as a last resort. Generally, WP installations can be saved with a little bit of know-how and elbow grease. Also note that it assumes that you’re switching domain names in the process. Also note that I wrote this in 10 minutes, off the top of my head – amendments or corrections welcome.

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For shorthand:
WPA is your old, corrupted installation
WPB is a brand new, totally empty installation of WP
WPC is your new production installation, on the new domain

The first step is to get your content out of WPA and into WPB. WPB should be a totally new, throwaway installation – a local installation would be ideal, but a fresh one on your webhost would be fine. (This should NOT be the same as WPC!!) Visit your WPA database (using PHPMyAdmin or whatever tool you’ve got), and export the following tables:
wp_posts
wp_postmeta
wp_comments
wp_commentmeta

In PHPMyAdmin, that usually just means checking the boxes next to those tables, and clicking an Export button somewhere in the interface.

Next, use PHPMyAdmin to view the database of WPB. Drop/delete the four tables corresponding to the ones you exported (wp_posts, wp_postmeta, wp_comments, wp_commentmeta).

Once these four tables are dropped, use PHPMyAdmin to import the versions you exported from WPA into WPB.

At this point, the posts should be safe and sound in WPB. You can verify by visiting WPB in your web browser. The next step is to use the WP export feature of WPB to get the posts out, in a format that WPC will be able to understand. Go to wp-admin on WPB > Tools > Export. Export everything to a local file. Then go to WPC Dashboard > Tools > Import (you may have to install the WP importer plugin) and import. This process should pull your old posts and pages in, without overwriting anything currently in your system.

It’s also a nice idea to set up a redirect from your old domain to your new one. (That will ensure that links to your old blog by other sites will continue to work, as well as any times you may have linked to your own old content.) Two steps:
1) At your domain registrar, make sure that your old WPA domain points to your WPC installation; this usually means putting the WPC domain as the CNAME attribute on the DNS tab.
2) FTP to WPC, and look for a file in the main WP directory called .htaccess (you may have to enable View Hidden Files or something like that). Near the top of the file, put the following lines:

[code]RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^myOLDdomain.com$ [NC]
RewriteRule ^.*$ http://myNEWdomain.com%{REQUEST_URI} [R=301,L][/code]

Make sure to replace myOLDdomain and myNEWdomain with the relevant domain names. This will redirect any request to myolddomain.com to the corresponding URL on mynewdomain.com, meaning that all your old permalinks should continue to work.