I am a java programmer and have been considering designing my own image hosting site. However, almost all of the free scripts I have found have been in PHP. Is there a reason for this? For this application is PHP more efficient?
Well, PHP is simple and open source. So many people have already done the wor with you. Typically all graphic manipulation scripts (CGI, PHP and even c#) utilize the same graphic library: GDI+ So as long as you make the component extensible you shouldn't have a problem.
I think he was moreso talking about the serverside aspects here, but regardless, PHP is generally the preferential choice. I don't think PHP being open source has much to do with it, also java is going to be open source "in months" one article I read said, but it doesn't make a big effect on the developers unless you're specifically trying to do something at a lower level. PHP usually runs a bit quicker as it's written in C/C++ so it's lower level than Java based programs. PHP is more common-place now, Java/JSP stuff is relatively "old" for the business and doesn't have quite as much support. I think the big thing is that any server can run PHP for the most part, Java means you have to go out and get tomcat or something else installed to run it so it isn't quite as versatile. In closing, go php
PHP scripts will just fit mostly on every hosting server that has PHP + GD Library /Imagemagick / Netpbm enabled. Easy to work with, no extended server specs required.