Error on local server

Hello,

when using the output in my own local server, it open menu.php and I get following message:

Fatal error: Uncaught Error: Call to undefined function mysql_connect() in C:\xampp\htdocs\Plots11\connections\MySQLConnection.php:71 Stack trace: #0 C:\xampp\htdocs\Plots11\connections\Connection.php(57): MySQLConnection->connect() #1 C:\xampp\htdocs\Plots11\connections\MySQLConnection.php(20): Connection->construct(Array) #2 C:\xampp\htdocs\Plots11\connections\ConnectionManager.php(26): MySQLConnection->construct(Array) #3 C:\xampp\htdocs\Plots11\connections\ConnectionManager_base.php(95): ConnectionManager->getConnection('Plots11_at_loca...') #4 C:\xampp\htdocs\Plots11\connections\ConnectionManager_base.php(115): ConnectionManager_Base->byId('Plots11_at_loca...') #5 C:\xampp\htdocs\Plots11\include\appsettings.php(861): ConnectionManager_Base->getDefault() #6 C:\xampp\htdocs\Plots11\include\dbcommon.php(90): include('C:\xampp\htdocs...') #7 C:\xampp\htdocs\Plots11\menu.php(6): require_once('C:\xampp\htdocs...') #8 {main} thrown in C:\xampp\htdocs\Plots11\connections\MySQLConnection.php on line 71

Any help available?
Kind Regards