Moving a website from one hosting provider to another is a process most developers and site owners face at some point. While many hosts offer automated migration tools, these conveniences can quickly become a source of nightmare when things don’t go as planned. This is the story of how a routine migration turned into a hunt for corrupted data, and how a simple PHP script saved the day—and the database.
TL;DR (Too Long; Didn’t Read)
The built-in migration tool of a well-known hosting provider corrupted serialized data during a WordPress website migration. Serialized strings became broken due to incorrect search and replace operations, leading to critical issues across the site. A custom search-replace script with serialized data support was used to fix the database. This experience highlights the importance of using tools that understand the structure of serialized data during migrations.
The Migration: A Routine Operation Gone Wrong
The site being migrated was a moderately complex WordPress installation loaded with custom post types, WooCommerce data, and dozens of plugins. The web host, known for its user-friendly interface, provided a “one-click migration” tool. The process promised a simple data transfer by just inputting FTP credentials and waiting a few minutes.
And so, the migration ran. Files were transferred, the database imported, and the host’s system even updated the base URLs automatically to reflect the new domain. Initially, everything appeared smooth—until the developer started testing the frontend.
Corruption Uncovered: Serialized Data and Broken Layouts
On loading the homepage, over half the widgets and theme options were missing. Product pages returned errors. Menu items disappeared, and plugin settings were wiped clean.
After enabling WP_DEBUG, the logs revealed the error: “unserialization failed: Error at offset x”. That led to a critical realization: the serialized data in the WordPress options table had been altered incorrectly. The base URL had been updated, but without preserving the string lengths that are vital in serialized strings.
To the uninitiated, serialized data is a structured way PHP stores complex arrays and objects in database fields. A sample serialized string might look like this:
s:23:"http://old-site.com";
If the domain were changed to a longer one like http://new-long-domain.com without updating the string length (which is 23 in this case), the entire serialized array becomes corrupted. PHP cannot unserialize it, and any configuration stored in that form—like theme settings or widgets—breaks.
The Blame Game: What the Host’s Tool Actually Did
The automated migration tool used a basic search and replace function to replace all instances of the old domain with the new one, regardless of where it existed in the database. This works fine in plain text, but serialized data requires more sophisticated handling. A simple string replacement rebalances the byte count in a way that breaks PHP’s ability to parse the string.
The most harrowing part? It wasn’t immediately apparent. Most fields corrupted this way are silently ignored on the frontend or fail gracefully. Without diving into logs or backend database checks, many site owners may never realize how much data silently got wiped or disabled during migration.
The Fix: A Safe Search-Replace Tool for Serialized Data
Faced with a partly unusable site, the developer had two options: roll back and do a manual export/import of the data or find a tool smart enough to update serialized strings correctly. That’s when they discovered the excellent open-source tool: Search Replace DB by interconnect/it.
This PHP-based script stands out because:
- It performs a database-wide search and replace
- It detects and adjusts serialized data lengths intelligently
- It provides a dry-run mode for testing before applying
- It comes with a simple GUI and terminal options
The developer uploaded the script via FTP, ran the interface from the browser, and input the old and new URLs. Within minutes of pressing “Go”, the database was scrubbed and cleaned properly, with no serialization issues whatsoever. The website’s widgets reappeared, menus returned, and plugins began functioning normally again.
Lessons Learned and Long-Term Takeaways
This experience highlighted several important points for developers and site owners migrating complex web applications:
- Understand what your migration tools actually do. If your host uses basic search-and-replace, it’s not safe for serialized data.
- Back up your entire WordPress installation—both files and database—before initiating any migration. This is critical for rollbacks if something goes wrong.
- Use tools that are built to handle serialized data correctly. Whether using WP-CLI, Serialized Search Replace DB, or another vetted tool, validate their capabilities before relying on them.
- Validate post-migration. Don’t assume all is well just because the homepage loads. Check logs, run diagnostics, and verify that settings, menus, and plugins are intact.
The Bigger Issue: Why Hosts Still Get It Wrong
For a process as simple as updating URLs in a string, it’s astonishing that many hosting platforms fail to account for complex data structures. The average WordPress database includes serialized arrays, JSON blobs, and nested configurations. A competent migration tool should parse each table correctly and adjust accordingly. That hosting providers are still offering replacements that corrupt databases is—even in 2024—a serious oversight.
Conclusion
This tale ends on a good note: the site was restored, users didn’t suffer, and a lesson was learned. But it serves as a cautionary reminder that behind any “quick” process lies hidden complexity. Developers who take the time to understand the structure of their data—and use the right tools—remain one step ahead of disaster.
Frequently Asked Questions (FAQ)
- What is serialized data?
- Serialized data is a way that PHP stores complex arrays or objects as a string format that includes data type indicators and string lengths. It is commonly used in WordPress for storing settings.
- Why does search and replace break serialized data?
- Simple text replacement does not update the length indicators in serialized strings. When lengths mismatch their actual content after replacement, PHP throws errors or fails to load the data.
- What tool can safely replace URLs in a serialized database?
- Search Replace DB by interconnect/it is one of the most popular tools. It automatically detects and updates serialized strings correctly.
- Is WP-CLI safe for search-replace operations?
- Yes, WP-CLI has a built-in
search-replacecommand with a--recurse-objectsflag that supports serialized data handling properly. - Should I trust hosting migration tools?
- Not blindly. Verify what their migration engine actually changes, especially when working with content management systems like WordPress. Always perform full backups before using them.
- What should I check after a site migration?
-
- Homepage and internal pages
- Navigation menus
- Widgets and theme settings
- Plugin functionality
- WooCommerce checkout (if applicable)
- Error logs
Ultimately, the migration was not just a change in hosting: it became a lesson in data integrity, tool literacy, and the value of a well-tested strategy for handling nuanced issues like serialized data in modern web development.
Published on November 22, 2025 under .
