When someone talks about PHP and drags up the old "but it doesn't scale well" argument, drop them an email with this new article from the O'Reilly ONLamp.com site that might change their minds. In it, they share some information they gathered (spurred on by James Gosling's comments on PHP a bit back) on how one large site, digg.com, has dealt with their huge popularity and scaling their PHP-based system.
They focus mainly on the cost of scalability - whether that be in hardware costs or simply in manhours. He interviews Owen Byrne, Senior Software Engineer for digg.com about some of his decisions on how to handle the explosive growth. They look at what "performance" and "scalability" really are, and some of Byrne's concerns on the matters as it pertains to PHP. They touch briefly on a few topics, including the hardware cost, the database cost, and the actual PHP coding cost of applications.
It turns out that it really is fast and cheap to develop applications in PHP. Most scaling and performance challenges are almost always related to the data layer, and are common across all language platforms. Even as a self-proclaimed PHP evangelist, I was very startled to find out that all of the theories I was subscribing to were true. There is simply no truth to the idea that Java is better than scripting languages at writing scalable web applications. I won't go as far as to say that PHP is better than Java, because it is never that simple. However it just isn’t true to say that PHP doesn't scale.
Pass it on...