Richard Blum

Working with PHP, MySQL, and JavaScript to create dynamic web applications can be difficult, but if you know a few programming tricks, you can make that job a lot easier. This Cheat Sheet shows you how to extract data from different databases in your PHP programs, filter out unwanted or potentially dangerous data from web forms, quickly find data stored in your MySQL database, and trigger timed events in your JavaScript programs.

SQL is a popular and useful programming language. You can make SQL even more useful if you know the phases of SQL development, the criteria for normal forms, the data types used by SQL, a little bit about set and value functions, as well as some tips on how to filter tables with WHERE clauses.Phases of SQL system developmentIn developing any system, you start at the beginning and go through to the end, and it’s no different with SQL.

The XMLHttpRequest object contains several class properties that you’ll need to know about to handle the HTTP response from the web server. The XMLHttpRequest Class Properties Property Description onreadystatechange Defines a callback function that the browser triggers when the HTTP connection changes state readyState Contains the connection status of the HTTP connection responseText Contains the response sent by the web server in text format responseXML Contains the response sent by the web server in XML format status Contains the numeric HTTP response code from the web server statusText Contains the text HTTP response string from the web server After you use the send() method to send a connection request to a web server, the HTTP connection process works through five connection states, as tracked by the readyState property: State 0: The connection has not been initialized.

The laser-guided miter tool for program development is the integrated development environment (IDE). IDE packages provide everything you could possibly need to develop any size of web application.Here are some of the advanced features IDE packages provide: Code completion: Start typing a code statement, and the package will provide a pop-up list of statements that match what you’re typing.

Linux can fulfill almost any need you have for the operating system on a desktop computer, but you must be able to tell it what you want to do in a way that it understands. You need to know common commands and how to access the help pages.Common Linux commands Command Description cat [filename] Display the file’s contents to the standard output device (usually your monitor).

Linux can seem like a very daunting environment. But it doesn’t have to be! With the two topics in this cheat sheet—the commands you’ll use on a daily basis and the useful help pages—you can easily navigate your Linux environment. © MIND AND I /Shutterstock.comLinux CommandsAlthough you can do most things in Linux these days by pointing and clicking, you still may want to try using Linux at the command prompt.

Troubleshooting is like reading a mystery novel. You have some facts, symptoms, and details, but you don’t know whodunit. You have to take whatever information you have, work with that data, weigh the various possibilities, and then narrow them to a single suspect. Finally, you need to test your theory and prove that your suspect is the guilty party.