For anyone that's wondered lately about the readiness of PHP for "enterprise applications", Norbert Mocsnik might just have the information you're looking for.

I'm always looking for good points that I can mention if someone asks me whether PHP is enterprise-ready or not. My primary interest in the industry is enterprise web portal development in PHP, so I was glad to read Marco's plans months ago. Hopefully he's still interested and works on this.

Today I found some convincing lines on the Zend website that one can use as a reference: "PHP has proven itself across a range of large enterprise deployments at companies worldwide including: Hewlett-Packard, Boeing, Lufthansa, Dresdner Bank, Disney Online, Yahoo!, Lycos, Sprint, T-Mobile, Orange, Nortel Networks, Lucent, WallStreetOnline and Siemens."

There's actually a discussion in the Sitepoint forums about Advanced PHP Programming in Corporate World for those of you who are interested.

With more and more companies out there opening their eyes to PHP (and the flexibility that it offers), it's no wonder that it's being considered more and more "enterprise-friendly". With the list mentioned above, there is definite grounds for recommendation to the higher-ups, especially those looking to save a bit on the bottom line. What PHP really needs (and every has been saying this for a while now) is one "killer app" that can really bring it out into the spotlight. Sure, there are frameworks and portals out there that do a good job of getting the work done, but there's still not much in the way of enterprise applications to speak of...