ERROR: Module mpm_event is enabled - cannot proceed due to conflicts. It needs to be disabled first! Considering conflict mpm_worker for mpm_prefork: ERROR: Could not enable dependency mpm_prefork for php7.2, aborting
I used sudo a2dismod mpm_event and received no errors. I restarted apache2 and then used sudo a2enmod php7.1 and it worked just fine.