What are the advantages of coldfusion over PHP?
Oh where to begin.......I could sit here all day listing the benefits.
The biggest benefit is that the MVC is much easier to control with coldfusion over PHP, yes you can use a nice MVC archetechture in PHP but you've got to know how to code it correctly, coldfusion simply makes this easier to deal with.
However I'm not saying Coldfusion is better then PHP and I'm not saying PHP is better then coldfusion, it all depends on what you want to do, the type of programmer you are ect...
Also there is no reason (Well other then your hosting provider) that you can't use Cold and PHP synchronously.
If you don't know MVC follow the link -
http://en.wikipedia.org/wiki/Model-view-controller and get with the 21st century.
EDIT: Just to toss this in I personally like Coldfusion because it gives a nice way to template your work (Again dealing with an MVC design), with PHP you can do this but I find it to be more tedious work then whats required with Coldfusion.
I actually find the large majority of things I do in Coldfusion takes me more time to do in PHP (PHP == 'slow' && Coldfusion == 'fast').
But again all depends on who you are, what you want to do, ect....
EDIT #2: Also forgot to say that using Coldfusion with Dreamweaver and other Adobe based products can really help excel your web development skills in so many ways.
P.S. I'm no expert in Coldfusion yet I only started learning and using it like 2 months ago but in that short period of time you can see how powerful it can be.