propably becouse php is free and hosting is cheaper so php is bether/cheaper for smaller projecs.
I heard There is some project creating reverse engeenering so sonn there shoulb be some free hosting on linux
C# is similar to AS in case of language syntax, but in case of framework is is similar only on basic level.
BTW
I had algorithm (about 300 lines of code) written in C# and I pasted code to Flash did some syntax changes, some minor type changes and in 1 hour i had AS version without even undetstanding how this algorithm exacly worked