As of today, mirrors are given a specific subdomain to host (such as ar.php.net). The problem with this concept is that quite often mirrors get either outdated, dead, unreachable, and so on, and people who are "aware of the mirror", either by directly accessing to it, or people linking to the mirrors directly, instead of the main website, get simply nothing when such thing happens.
If a mirror have serious problems, our system disables it right away, and we see those problematic mirrors. If you visit the mirror management page, you can see that we have very few mirrors with long lasting problems. Most of the problems are only affecting mirror acess for a few minutes/hours.
Instead of having each mirror under a specific "number" in an array of a country, install all the mirrors as "countrycode.php.net", and use a smarter system than the current one, that will look up the IP of the CNAME that people give every once in a while (a day, for instance), and then try to contact all the mirrors according to the IP against the countrycode name. Given the "the mirror on this IP is working" status code, generate the subdomain of php.net with that IP, too.
Given *no* IPs are return to have positive responses, point the subdomain to the PHP.net master mirror (or any other US mirror, whatever is decided).
Do you mean this on the DNS level? That was discussed heavily before...
This new concept also helps spreading the load on countries who has numerous mirrors (i have a reason to believe that currently only the first mirror is utilized).
One mirorr is selected randomly from the same country, see the code yourself (include/loadavg.inc)...
Goba