"Hewlett-Packard, Boeing, Lufthansa, Dresdner Bank, Disney Online, Yahoo!, Lycos, Sprint, T-Mobile, Orange, Nortel Networks, Lucent, WallStreetOnline and Siemens."
This helps answer the question, "Who are the enterprise?" but raises another: "Where have they been?"
My experience so far has been that corporations keep plans to implement open source technology tightly guarded under non-disclosure agreements. Upon discovering I was, "an open source guy" a friend of a friend with a wink and a nudge disclosed to me that his company uses MySQL as the mainstay of their information gathering operations. Huge operations. Yet he'd throttle me if I disclosed the company name (a household word in IT).
Why the shame?
At least here in the USA, it seems that corporations are as embarrassed to admit to using open source technology as they are to outsourcing jobs. The mentality is almost as if PHP programmers are "stealing" jobs from ASP/JSP programmers, and MySQL is encroaching on the livelihood of good old Oracle admins. The perception that open source tools are somehow less expensive and therefore must be of lesser quality has to go. The cowboy coders and fly-by-night programming shops only exacerbate this perception.
In my career I have seen time and again that PHP, done right, is ready for the enterprise. When will the enterprise be ready for PHP? Imagine the day when a gathering of CEOs at a well-heeled luncheon are bragging about their, "1,000 node PHP 5 server farm backed by a 100 node MySQL 5 cluster", slapping their senior PHP Quality Assurance Director on the back for keeping everything ship-shape, and sending their best people in droves to PHP Conferences with as much razzle and dazzle as Apple's WWDC or Lotusphere.
Then we will know PHP has pulled the sword from the stone, and claimed its rightful place. Until then, we've got work to do.