Why phpMyAdmin migrations break plugin settings — and why `wp search-replace` doesn’t

After a domain migration or HTTPS switch, "all plugin settings are gone" or "Elementor layouts are broken" is a common outcome. The cause, in most cases, is running a string replacement against the WordPress database without accounting for PHP serialized data. WordPress stores plugin configurations, custom field values, and widget settings in PHP’s serialized format. Standard SQL replacements — phpMyAdmin’s find-and-replace, raw UPDATE statements, sed on a .sql dump — rewrite the string value without updating the length metadata that serialization embeds alongside it. The result is a database that appears intact but returns false on every read of the affected values. wp search-replace handles this correctly. Understanding why makes the pre- and post-execution steps more deliberate. What PHP serialization stores alongside the value A serialized entry in WordPress looks like this: a : 2 : { s : 4 : "home" ; s : 22 : "http://example.com/top" ; s : 5 : "title" ; s : 8 : "My Site" ;} The segment s:22:"http://example.com/top" means "a string of 22 bytes." The s:N: prefix records the byte length. When a simple string replacement changes http://example.com to https://example.com : Before: s:22:"http://example.com/top" (22 bytes) After: s:22:"https://example.com/top" (23 bytes) The s:22 stays unchanged even though the actual string is now 23 bytes. PHP’s unserialize() detects this mismatch and returns false . The plugin reads false instead of its configuration array and behaves as though the settings were never saved. phpMyAdmin’s find-and-replace executes a SQL UPDATE at the storage layer. No PHP context exists there — it can’t know the column contains serialized data, and it doesn’t adjust the length prefix. How wp search-replace handles it wp search-replace operates at the PHP layer, not the SQL layer: Reads each column value Checks whether it’s serialized using is_serialized() If serialized: calls unserialize() to expand it into a PHP array or object Applies the string r