1. Key Difference 1: Syntax and Language Features: Adobe ColdFusion uses a tag-based syntax similar to HTML, which allows developers to easily integrate with existing HTML code. PHP, on the other hand, uses a syntax that is more similar to traditional programming languages like C and Perl. This difference in syntax and language features makes ColdFusion more accessible for web designers who are familiar with HTML, while PHP is often preferred by developers with a programming background.

2. Key Difference 2: Platform Compatibility: Adobe ColdFusion runs on Java, which means it can be deployed on any platform that has Java support. On the other hand, PHP is a server-side scripting language that is specifically designed for web development, and it can be easily integrated with popular web servers like Apache and IIS. This difference in platform compatibility allows ColdFusion to be used in a wider range of scenarios, while PHP is often the preferred choice for web-based applications.

3. Key Difference 3: Community and Support: PHP has a larger and more active community compared to Adobe ColdFusion. The PHP community provides extensive documentation, tutorials, and forums, making it easier for developers to find help and resources when they encounter issues or need to learn new concepts. ColdFusion, although it has a dedicated user base, lacks the same level of community support and resources as PHP.

4. Key Difference 4: Performance and Scalability: PHP has proven to be more performant and scalable than Adobe ColdFusion in many scenarios. PHP's lightweight nature and efficient memory utilization enable it to handle high traffic websites with ease. ColdFusion, on the other hand, can experience performance issues with large-scale applications due to its heavier resource requirements and less efficient memory management.

5. Key Difference 5: Learning Curve and Developer Skills: PHP has a relatively low learning curve compared to Adobe ColdFusion. Many developers are already familiar with PHP or come from a background in programming languages using similar syntax, which allows them to quickly adopt and start working with PHP. ColdFusion, on the other hand, requires developers to learn a specific tag-based syntax and its unique features, which can take more time and effort to master.

6. Key Difference 6: Cost: Adobe ColdFusion is a commercial product, and the licensing costs associated with it can be a significant factor for organizations considering its adoption. PHP, on the other hand, is an open-source language, and there are no licensing fees involved. This cost advantage makes PHP a preferred choice for small businesses and startups with limited budgets.

In Summary, Adobe ColdFusion and PHP differ in their syntax and language features, platform compatibility, community support, performance and scalability, learning curve and developer skills, as well as cost. While ColdFusion is more accessible for web designers and offers wider platform compatibility, PHP has a larger community and better performance.