October CMS – How To Fix Broken Thumbnails

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I recently started setting up a dockerized October CMS environment based on Alpine Linux, MariaDB and PHP-FPM which was actually a very straightforward process. However, for some reason the integrated image resizer didn’t create thumbnails of uploaded images.

October CMS - Broken Thumbnail Image

Unfortunately there was nothing in the log files which could help me to identify the cause of the problem. After checking the file permissions, I decided to trace back the issue and found the reason in file vendor/october/rain/src/Database/Attach/Resizer.php.

The method getMimeType() returned always null, which broke the entire image manipulation process.

After a quick research I found out that getMimeType requires php_fileinfo which I simply forgot to set in my Dockerfile. After adding php7-fileinfo and rebuilding the container, the issue was finally fixed.