5. The JavaScript then places an indication next to the username input box to show whether the name is one available to the user—perhaps a green checkmark or a red cross graphic, along with some text. 6. If the username is not available and the user still submits the form, the JavaScript interrupts the submission and reemphasizes (perhaps with a larger graphic and/or an alert box) that the user needs to choose another username. 7. Optionally, an improved version of this process could even look at the username requested by the user and suggest an alternative that is currently available | 5. The JavaScript then places an indication next to the username input box to show whether the name is one available to the user perhaps a green checkmark or a red cross graphic along with some text. 6. If the username is not available and the user still submits the form the JavaScript interrupts the submission and reemphasizes perhaps with a larger graphic and or an alert box that the user needs to choose another username. 7. Optionally an improved version of this process could even look at the username requested by the user and suggest an alternative that is currently available. All of this takes place quietly in the background and makes for a comfortable and seamless user experience. Without using Ajax the entire form would have to be submitted to the server which would then send back HTML highlighting any mistakes. It would be a workable solution but nowhere near as tidy or pleasurable as on-the-fly form field processing. Ajax can be used for a lot more than simple input verification and processing though we ll explore many additional things that you can do with it in the Ajax chapters later in this book. In this chapter you have read a good introduction to the core technologies of PHP MySQL and JavaScript as well as Apache and have learned how they work together with each other. In Chapter 2 we ll look at how you can install your own web development server on which to practice everything that you will be learning. Test Your Knowledge Questions Question 1-1 What four components are needed to create a fully dynamic web page Question 1-2 What does HTML stand for Question 1-3 Why does the name MySQL contain the letters SQL Question 1-4 PHP and JavaScript are both programming languages that generate dynamic results for web pages. What is their main difference and why would you use both of them Question 1-5 If you encounter a bug which is rare in one of the open source tools how do you think you could get it fixed See the section Chapter 1 Answers on page 435 in .
