Good morning!

I have been running Pwigo for years with no problems under PHP 7.4.
My provider just let me know that it is approaching end-of-life later this year, and that I should upgrade to a more current version.  I have done no customization, it is a stock Pwigo system.

I have tried both PHP 8.0 and 8.1, and I get all sorts of error messages like this:

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Deprecated: strip_tags(): Passing null to parameter #1 ($string) of type string is deprecated in /webroot/g/r/gregp001/pyros/www/gallery/include/functions_html.inc.php on line 534

(this message repeats about 100 times)

Warning: Cannot modify header information - headers already sent by (output started at /webroot/g/r/gregp001/pyros/www/gallery/include/functions_html.inc.php:534) in /webroot/g/r/gregp001/pyros/www/gallery/include/page_header.php on line 94

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /webroot/g/r/gregp001/pyros/www/gallery/include/template.class.php on line 911
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Environment
    Piwigo 12.3.0 Check for upgrade
    Operating system: Linux
    PHP: 7.4.27 (Show info) [2022-07-20 08:38:26]
    MySQL: 5.5.5-10.4.22-MariaDB-1:10.4.22+maria~buster [2022-07-20 15:38:26]
    Graphics Library: ImageMagick 6.9.12-34
    Cache size 1523.05 Mo   calculated 2 minutes ago Refresh

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Piwigo URL: https://www.pyros.com/gallery
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Is this a known issue?  Any ideas as to how to fix it?  I went back to PHP 7.4 until we can get this figured out!

Thanks for any ideas,
Greg