robustness and stability would both be properties of the language interpreter (mod_php, cgi, fastcgi...)
mod_php is stable enough for what it is... robustness is arguable... mod_php might not scale but it's a key component in php's popularity because it's a zero configuration plugin for apache that works perfectly for the needs of 90% of people writing php or running php applications.
mod_php is stable enough for what it is... robustness is arguable... mod_php might not scale but it's a key component in php's popularity because it's a zero configuration plugin for apache that works perfectly for the needs of 90% of people writing php or running php applications.