先安装一下这个命令 add-apt-repository
apt-get install software-properties-common

添加第三方源:
add-apt-repository ppa:ondrej/php
apt-get update

安装php:
apt-get install php7.4 php7.4-fpm php7.4-mysql php7.4-gd php7.4-mbstring
service php7.4-fpm start
php -v

[PHP] Ubuntu快速安装起PHP7.4_PHP

nginx的配置文件和原来一样

server {
    listen       80;
    server_name  localhost;
    access_log  /var/log/nginx/default.access.log  main;
    error_log /var/log/nginx/default.error.log;
    root   /var/www/html;
    location / {
        index  index.html index.htm;
    }
    location ~ \.php$ {
        fastcgi_pass   127.0.0.1:9000;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
        include        fastcgi_params;
    }
}

[PHP] Ubuntu快速安装起PHP7.4_PHP_02