All,

The subject error occurs intermittently.  DreamHost support suggests someone on this forum might have an idea of what could cause this.  The entire message displayed:

Fatal error: Uncaught Error: Call to undefined function get_nb_available_tags() in /home/dick/photos.hodgman.org/html/piwigo/include/menubar.inc.php:298 Stack trace: #0 /home/dick/photos.hodgman.org/html/piwigo/include/menubar.inc.php(15): initialize_menu() #1 /home/dick/photos.hodgman.org/html/piwigo/index.php(103): include('/home/dick/phot...') #2 {main} thrown in /home/dick/photos.hodgman.org/html/piwigo/include/menubar.inc.php on line 298

When the error is displayed, it recurs on refresh and on reload, and sometimes the correct content is later displayed spontaneously.  A later reload can return the correct content, or the error. 

https://photos.hodgman.org/piwigo/

I suspect a server problem, but do not have access to the server logs, only to the logs for my website.  The website error log shows the above text as the first error. 

Thanks for your help.