//安装php7.3
apt-get install php7.3
//禁用php7.0
a2dismod php7.0
//启用php7.3
a2enmod php7.3
//重启apache2
service apache2 restar
//安装php7.3
apt-get install php7.3
//禁用php7.0
a2dismod php7.0
//启用php7.3
a2enmod php7.3
//重启apache2
service apache2 restar
原文：https://www.cnblogs.com/woshixiaozhu/p/14009749.html