Values in single quotation marks are treated literally, whereas those within double quotation marks will be interpreted.

Basic ways to debug PHP include:
Making sure you are always running PHP scripts through a URL
Know what version of PHP you're running
Make sure display_errors is on
Check the HTML source code
Trust the error message
Take a break!

The $_SERVER variable referes to a mass of server related information.
The type of information it can hold includes the full file path of the script.
What browser and operating system the user is using.
And the web application on the server that is running the PHP.

Length of full name: 21
Normal case for full name: Everett Taylor Wilcox
Uppercase of full name: EVERETT TAYLOR WILCOX
Lowercase of full name: everett taylor wilcox

The Quotient of 9/7 rounded to the first four decimal places is: 1.2857
3005 with a comma after the three is: 3,005

My full name is Everett Taylor Wilcox, My current age is 16, My birth year is 2007, The color of my eyes are Brown Eyes.

Plain text: $char
Interpreted HTML: Hello World