A fatal error has occurred

Error text:

Uncaught Error: Call to undefined function ereg_replace() in /customers/d/3/6/domareforbundet.se/httpd.www/site-admin/chimera/func.php:52 Stack trace: #0 /customers/d/3/6/domareforbundet.se/httpd.www/site-admin/modules/cal.php(164): normalise_removespecialcharactersonly('Arsmote 2020') #1 /customers/d/3/6/domareforbundet.se/httpd.www/site-admin/modules/cal.php(238): one_event(Array) #2 {main} thrown

In the file /customers/d/3/6/domareforbundet.se/httpd.www/site-admin/chimera/func.php at row 52