PHP is cheaper to implement that ASP.
PHP gives us additional capability than if we were to code with ASP.
We are strong proponents of the “Open Source” movement. Open source software is a collaborative effort amongst a worldwide community of volunteer programmers with a passion for technology. People of disparate backgrounds and experiences join together to solve problems in new ways, thus resulting in better software.
Open source software is free to use, copy, and modify, which makes it a great deal for our clients.
It is also highly flexible, because it allows us to extend the software and customize it for our clients’ requirements.
We don’t have to reinvent the wheel when we embark on a project for a client, as there is an amazingly extensive library of software written in PHP that’s free and available in source code form. Whenever possible, we repurpose our own extensive code library. But if we haven’t already built a similar web application before, we look for the best open source software to meet the functional requirements and pick up where that software left off. Adding such enhancements and customizations to the software’s source code wouldn’t be possible with proprietary closed-source software.
There are no requirements to purchase commercial licenses and pay continuously for upgrades. For example, to perform binary file uploads, retrieve a file via FTP or HTTP, encrypt passwords in MD5, or send email from a Web page require 3rd party commercial software packages in ASP. It’s all available for free in PHP.
PHP is platform-agnostic
It will run on Linux, Solaris, Windows, and other operating systems as well. With ASP you’re also forced down a path that is very costly and painful to extricate yourself from. For example, what if you wanted to switch web hosting providers to one that was more reliable and had better customer service but was Linux-based? ASP only runs reliably on Microsoft Windows-based web servers.
PHP is the most popular web programming language on the planet
It’s more popular than ASP, Cold Fusion, Perl, or any other web programming language.
All else being equal, PHP is faster than ASP
ASP supports multiple programming languages. This architecture is inherently slower and more memory intensive that PHP’s model because each ASP language compiler runs in its own process. So when ASP detects a Begin ASP tag () it will do a context switch back to the HTML parser.
PHP is secure
IIS Server is notorious for its security holes.
Coding in PHP is more efficient than in ASP
Typically the same functionality can be accomplished in less code with PHP than with ASP. This is because the HTTP GET and POST variables are created automatically by PHP as global variables, thus eliminating the step of extracting them from the ASP Request object. PHP’s HTTP header manipulation functions are easier to use than in ASP.
More justifications can be found at http://php.weblogs.com/php_asp_7_reasons