nginx reverse proxy not working code example

Example 1: pass proxy nginx

location ~ \.php {
    proxy_pass http://127.0.0.1:8000;
}

Example 2: nginx reverse proxy multiple folders

location ~ ^/app1(.*)$ {
    proxy_pass http://proxy.example.com$1;
}

-OR-

location /app1 {
    proxy_pass http://proxy.example.com/app1;
}