Serialized Data in WordPress
Developers often choose to store specific information in the database like theme options, or settings. Typically this data is serialized in the database so it can be copied or restored easily without compromising the integrity of the information.
About Serialized Data
“Serialized data” is just a fancy way of saying “to list data in a specific order”. PHP has a function called
serialize() which stores data as a serialized row in the database. For example the “active_plugins” row in wp_options of your database may look like this:
That probably looks like a lot of nonsense, but in reality it’s just taking a list of items and placing it on a single row. The array has a total count of items, each item has a number in the sequence, and each item has a total count of characters.
a:8 = There are 8 items in this array
i:0 = This is item 1 in the array (counting begins with zero)
s:31 = This item has 31 characters
query-monitor/query-monitor.php = The value of the item is located in quotes. The number of characters here should always match the numerical value proceeding it.
You can also break the single line out into multiple lines for easier reading. Just be aware that it must be on a single line if copied back into the database.
$array = array(
'0' => 'query-monitor/query-monitor.php'
'1' => 'accesspress-instagram-feed/accesspress-instagram-feed.php'
'2' => 'akismet/akismet.php'
'3' => 'easy-captcha/easy-captcha.php'
'4' => 'google-analytics-dashboard-for-wp/gadwp.php'
'5' => 'instagram-feed/instagram-feed.php'
'6' => 'jetpack/jetpack.php'
'7' => 'really-simple-captcha/really-simple-captcha.php'
The most common conflict occurs when copying your site to a different environment, as this will change the domain. If your site uses serialized data in a row that contains the domain the character count will no longer match the updated value.
For example, say your site stores serialized data in a row with the URL in it, like this:
Notice that the value of this item has 23 characters, and is denoted by
s:23 in the array.
If copied using one of our Copy Site tools, the URL is search and replaced automatically to the new domain value. That means that the same row on your new environment would end up like this:
But after this change, the value is now 27 characters long meaning
s:23 is incorrect. This invalidates the array and the entire row.
So for example, if your theme options stored a full URL path for some settings or an image, it would end up showing default theme settings on the site instead of your custom theme and settings.
If you are performing a basic SQL search/replace on your site, it won’t be able to intelligently update these rows containing serialized data, because it can’t automatically update the character count.
However, if you are performing a search and replace with PHP, this will work for serialized data.
When copying sites, there are a few options to search using PHP, so as to not break the serialized rows:
- The Better Search Replace plugin automatically handles serialized data
- The Search and Replace plugin offers an option which handles serialized data
If you are running into issues with broken serialized data even when using one of the above methods, often times themes or plugins which store important data as serialized rows will offer an export option. With this option, you can export the settings, then import them to the new environment to fix the issue.