Bits of .NET

📝 A Theme Update Just Erased the Custom Code You Added to functions.php

Custom code – a snippet for tracking, a small tweak to how something displays – gets added directly to the active theme’s `functions.php`, and it works perfectly until the next theme update completely overwrites that file with the theme author’s original version, silently discarding every custom edit, because theme updates replace theme files wholesale rather than merging changes into them.

🔎 Why This Happens

[“A WordPress theme update works by replacing the theme’s files with the new version’s files – it has no way to know which lines in `functions.php` were the theme author’s and which were your own additions, so an update simply overwrites the whole file with the new official version, custom code included in the loss.”, ‘This is a documented, expected behavior of the WordPress theme system, not a bug in the update mechanism – the fix is architectural (where custom code lives), not something to work around update by update.’]

✅ Fix: Move Custom Code Somewhere an Update Can’t Touch

• Use a CHILD THEME for any custom code meant to persist – a child theme’s own `functions.php` is never touched by parent theme updates, since it’s a genuinely separate theme that inherits from the parent rather than a copy of its files.
• For code that isn’t tied to appearance at all (tracking snippets, small functional tweaks), a small SITE-SPECIFIC PLUGIN is often the more robust choice over a child theme – it survives not just theme updates but a full theme SWITCH too, since it’s decoupled from the theme entirely.

⚠️ Recovering What Was Just Lost

• Check for a recent site backup taken before the update – most managed WordPress hosts keep automatic pre-update backups specifically for this scenario, and restoring just the previous `functions.php` (not the whole site) from one is usually enough.
• If no backup exists, check whether the same custom code is referenced anywhere else – a support ticket where it was originally shared, a code snippet manager, version control if the site is tracked in one – since recreating custom code from memory is far more error-prone than recovering the original.