PHP and DHTML
DHTML is HTML that includes JavaScript code that changes the content or layout of the page in the browser without going back to the server. When you write an HTML page, you're actually writing an object tree. All the tags become objects in the JavaScript space. Using JavaScript, you can change their content, Cascading Style Sheets (CSS) styling, and location - all without ever going back to the server. DHTML is the intersection of HTML, CSS, and JavaScript:
PHP and DHTML, Part 1