I think a big problem here is that there is no such thing as a 'typical php/mysql CMS environment', let alone a typical hosting environment. Things will vary enormously I think.
On a raw level I recall that Litespeed have said that the 150 connection limit should be enough to serve several miilion hits per day.
This makes sense when you do some [very crude] maths (eg if one connection serves up three hits and lasts 15 seconds, 150 concurrent connections = 600 connections/min serving up 1800 hits/min = about 36000 connections/hour serving 108000 hits/hr = 2.5m hits/864,000 connections per 24hrs).
The 150 theoretical concurrent connections up front to your web-server may only the tip of the iceberg, however.
If those 150 concurrent connections are going through to a PHP app that is then sending many of those connections through to a database, you'd have to think about that too. The chances are very high that the database will be more demanding of system resources than the web server.
The 150 connection limit is a hard ceiling - if you are thinking of a 150 concurrent connections *average* peak, as opposed to 150 connections absolute peak load, you already need the Enterprise Edition otherwise you will potentially be dumping a lot of traffic.
Last edited by brrr; 07-12-2008 at 06:48 PM..