Exception - Call to undefined function mysql_connect()

Error code: generalexceptionmessage
Stack trace:

line 461 of /lib/adodb/drivers/adodb-mysql.inc.php: Error thrown
line 492 of /lib/adodb/drivers/adodb-mysql.inc.php: call to ADODB_mysql->_connect()
line 652 of /lib/adodb/adodb.inc.php: call to ADODB_mysql->_nconnect()
line 165 of /auth/db/auth.php: call to ADOConnection->Connect()
line 111 of /auth/db/auth.php: call to auth_plugin_db->db_init()
line 4180 of /lib/moodlelib.php: call to auth_plugin_db->user_login()
line 144 of /login/index.php: call to authenticate_user_login()