ASP is Microsoft-centric. Programs written in ASP.Net run on Microsoft IIS servers, rather than the Apache (Unix, Linux, etc…) servers which comprise the overwhelming percentage of web servers on the Internet. Big corporations who have ties to Microsoft tend to use their products, and would use ASP.Net along with SQL Server (another Microsoft offering).

I would like to suggest a good book for you to look at. This is the book I bought when I started learning myself:

Build Your Own Database Driven Website Using PHP & MySQL
by Kevin Yank

It is exceptionally well written and covers PHP very well, along with MySQL. (You will need to learn databases too when you tackle tougher projects.)

You can read the first 4 chapters free using the first link shown. Or, you can buy it on-line. Amazon.com also sells it (second link).

For a start, I'm sure GMail uses Asynchronous Javascript And XML (AJAX). This allows it to transparently display dynamic data without refreshing the entire page. Google's search engine itself is based on C/C++ … if I'm not mistaken. You can read their research papers on their website regarding their PageRank technology (it claims certain parts are in C/C++). I would think that GMail would be using PHP or Java .. but more likely than not, it would be PHP because it's faster to develop in.

It's hard to tell really … we could send them an email to ask. But it's a very interesting question which I would like to know the answer to too.

For IIS you almost always see ASP.Net. This also comes in a Web Services flavor.

Right now Apache has a little over 50% market share, while IIS runs around 35%.

PHP is generally easier to learn, easier to host, easier to get support for and more forgiving of mistakes.

ASP.NET is best for enterprises that are wedded to Microsoft products.

On that note, web servers have the ability to change the extension of the file you are accessing if the programmer of the website so desires. It is common for a developer to use Apache's mod_rewrite module, which is a rewrite engine, to change the extension of .php files to .html. You can find more information on rewrite engines at http://en.wikipedia.org/wiki/Rewrite_engine.

When building web sites, ASP and PHP are very popular languages. Here's my opinion on whether ASP or PHP is best.

Both ASP and PHP are languages used to build Dynamic Web sites that can interact with Databases and exchange information. ASP (Active Server Pages) is from Microsoft and is used with IIS (Internet Information Server) that runs on Microsoft Servers. PHP (PHP: Hypertext Preprocessor) is from Rasmus Lerdorf, who originally designed this parsing language which was later modified by different people. It runs on Unix and Linux servers and it also has an NT server version.

There are a lot of differences between ASP and PHP.

Cost

To run ASP programs one needs IIS installed on a Windows platform server, which is not free. PHP programs run on Linux, which is free. Even the connectivity of the database is expensive in the case of ASP as MS-SQL is a product of Microsoft that needs to be purchased. PHP generally uses MySQL, which is freely available.

Speed

If we compare the speed of ASP and PHP then PHP has an upper hand. PHP code runs faster than ASP. ASP is built on COM based architecture, which is an overhead for the server whereas PHP code runs in its own memory space.

Platform Compatibility

PHP programs can run on various platforms like Linux, Unix, Windows and Solaris whereas ASP is mainly associated with Windows platforms. However, ASP can run on a Linux platform with ASP-Apache installed on the server.

Additional Costs

Many of the tools used in PHP are free of cost and since PHP is open source a lot of code can be found in open source forums. PHP has inbuilt features like ftp, email from a web page or even encryption mechanisms but in ASP such features are not built in and some additional components are required. Therefore an additional cost is incurred for such components.

Base Language

PHP is based on C++ language and the syntax used in PHP is quite similar to C/C++. C/C++ is still considered the best programming language by many programmers and people who love this language would surely feel more comfortable with the syntax of PHP. ASP on the other hand has a more Visual Basic kind of syntax that again is closely related to only Microsoft products. So, it depends on a person-to-person which language he or she is comfortable

Database Connectivity

PHP, being extremely flexible, can connect to various databases, the most popular being MySQL. ASP mainly uses MS-SQL.

Conclusion

Both languages have their advantages specific to users. Some would argue that both the languages have their own importance and depending on the user's requirements the language and the platform can be chosen. If we talk about developing a discussion board then ASP is equally capable but many feel the best discussion boards are developed in PHP. If a user is looking for some e-commerce application development then many would call ASP the ideal choice. This does not mean that PHP cannot provide e-commerce solutions, only that many people choose ASP.

From my perspective, PHP is an all around better choice than ASP