Core technologies, there purpose, and why we use HTML & CSS, Javascript & jQuery and PHP & MySQL

HTML and CSS - Hypertext Markup Language & Cascading Style Sheets

Hyper Text Markup Language (HTML) is the key way to present content on web pages, the HTML elements are placed onto web pages to build up a websites structure.

The HTML elements on a web page are defined by tags, usually having a start tag <p> p for paragraph tag, and a closing tag </p>. These tags tell a web browser how to interpret the HTML. Providing web users with the information they require.

The tags are not displayed but tell a web browser what something is or how it should be displayed. For example, an <img> tag to show an image or a <h1> </h1> tag to show web page headings.

These HTML elements can also be linked to Cascading Style Sheets (CSS) to tell a web browser how to style the appearance of web pages.

The World Wide Web (W3C) consortium encourages this standard of HTML & CSS as a way to ensure uniformity across the web.

Javascript and jQuery

Javascript is a scripting language that helps create interactive websites, through the use of dynamic content, and runs on the web browser.

jQuery is a multi-browser JavaScript library designed to simplify the creation of dynamic and interactive web content.

jQuery is free, open source software, and is designed to make it easier to find and manipulate elements and events on a web page.

jQuery also, overcomes the need to refresh pages to view updated content. For example, it could be used to catch a mouse click on a certain area of a page that will then tell the web browser to hide or display some web content or pictures.

The rotating images at the top of this page, show how jQuery fades images constantly without the need for the page to be refreshed.

PHP & MySQL

PHP is a server-side scripting language; the server processes PHP commands – not the web browser. PHP has been created to aid web development and produce dynamic web pages.

The PHP works by being inserted, embedded, into a html web page's source code and then the PHP functionality is interpreted by a web server that has a PHP processor module. This means events on a web page or user interaction can trigger PHP scripts to run. For example, a user adds an item to a shopping basket and PHP stores this information in a database for future reference.

PHP is free and can generally be installed on all operating systems and web server platforms, which makes it highly available.

MySQL is a relational database management system providing access to stored data. A relational database means relationships are formed between pieces of data so all data should be meaningful.

For example, you should not be able to store an order for a product on an ecommerce website if that order is not related to a customer. Likewise you should not be able to delete a customer from a database if they have an order related to them. This ensures the integrity of the database is always maintained.

Many web applications use PHP and MySQL in partnership to provide feature rich websites: Joomla, WordPress and phpBB are all successful web applications that are highly available due to them being free and easily installed on web servers.

Wikipedia, Google, Facebook and Twitter are all believed to use, in different scenarios, these applications.