There has been a lot of Discussions about Enterprise PHP, specially after the release of PHP 5. PHP has a much better Object Model now, butt PHP is still NOT enterprise ready.

The first step toward enterprise is PHP's emancipation from Apache Web server. Since 4.1.0 Version, PHP supports sockets. Therefore PHP itself can serve HTTP Requests. Although PHP sockets are experimental, but it really rocks. I have written a simple IRC Sever in PHP using PHP sockets and it is up since about 70 days.

There are some greats apps using PHP Sockets. The best example I know is nanoweb. (Has anyone tested nanoweb under a heavy load?), but I miss some kind of "PHP-Container", like a servlet container, PHPlet is the first effort.

Until PHP is not able to have persistence between request, it hard to speak form Enterprise PHP. Persistence database connection and memory held session data beyond the hardware are the crucial disadvantages of PHP against Java.

memcached and Vulcan SRM are great efforts, but they are not the solution.