A dif­fer­ent kind of migra­tion — pub­lic domain from Wiki­pe­dia Commons

When you move a Word­Press blog from one folder to another, or from one site to another, you nor­mally use the export/import functionality.

This is fine for nor­mal blogs, but say you’ve developed a new web­site and set it up on your local machine — the URL for the site may be some­thing like http://localhost/devsite and the live URL will be some­thing like http://www.davesgonemental.com — you won’t want to set up all the theme options, site options, plu­gin options and so on all over again.

Instead, a the­or­et­ic­ally simple approach is to do a data­base dump, a search and replace for all ref­er­ences to server paths and URLs, and then reim­port that data in the new location.

Should work, but it often falls apart.

What hap­pens is that in Word­Press, its themes and its plu­gins, a lot of data is stored using a method known as seri­al­iz­a­tion.  Now, in my opin­ion this breaks all known good prac­tice around data — it’s lan­guage spe­cific, it’s not rela­tional even though it often could be, and it’s hard to edit by hand.

One par­tic­u­lar prob­lem is that if you change the length of the data in a seri­al­ised string you have to change the length declared in the gen­er­ated string.

That’s very pain­ful when you have hun­dreds of the fields.

So, because I’d found this pain­ful I decided to knock together a quick applic­a­tion to at least reduce the amount of edit­ing I had to do.  You just do your search and replace, for­get about the seri­al­ized string lengths, upload your data to the new data­base, and run this script.

Warn­ing: I haven’t got it to work for wid­gets and cForms II yet, but the lat­ter has some export func­tion­al­ity any­way, which takes that par­tic­u­lar pain away if you plan ahead.  In the mean­time, feel free to play with the attached file.  You use it at your own risk, of course.

To use it, down­load the file linked in this post, extract it, open the file, edit the con­nec­tion set­tings, tell it the table you want to scan through, the column, and the unique key field.  If you some­how man­age to have more than one unique key to deal with (you shouldn’t, but then it sur­prises me what people man­age to code up), then you’ll have to modify the code accord­ingly.  Once done, make sure you have a backup of that table, and execute the php — either at the com­mand line or through the browser. License is WTFPL, and if you’d like to improve the code, please do and I’ll host the new version.

down­load file

Serialization-fixer.zip down­load

BIG WARNING: I take no respons­ib­il­ity for what this code does to your data. Use it at your own risk. Test it. Be care­ful. OK? Here in the North we might describe the code as being as “Rough as a badger’s arse.” Never felt a badger’s arse, but I’ll take their word for it.

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