> > geo $y {
> > default "${precision}+1";
> > }
>
> - with fastcgi_param PHP_VALUE "precision=$x";
> + with fastcgi_param PHP_VALUE "precision=$y";

I do not think PHP-FPM can perform inline mathematical evaluation within passed arguments to PHP_VALUE/PHP_ADMIN_VALUE. But it works for me when it comes to generic substitution of existing and defined in the master php.ini file configuration variables, with their actual values. In my experience, Maxim's suggestion works fine, and I could so far reference any variable I wanted in the PHP configuration file. This is very useful, for example, if you want to set security limits with open_basedir, but you also want to make sure that uploads work, but you don't want to hardcode the temporary upload folder into open_basedir, but rather read the current value from php.ini by adding ${upload_tmp_dir} to open_basedir value in the nginx configuration using fastcgi_pass PHP_ADMIN_VALUE:

geo $upload_tmp_dir {
default "${upload_tmp_dir}";
}
...
fastcgi_pass PHP_ADMIN_VALUE "open_basedir=$document_root:$upload_tmp_dir";

Anyway, it works for me.

Andrejs