Server Side Verses Client Side
The difference between server and client side operations is a very important concept to understand when it comes to designing the architecture of a web site.
SERVER SIDE VS CLIENT SIDE
Simply put there are two distinct operations involved in displaying any web page to the visitor the first being server side operations and the second client side operations.
Server Side Operations
PHP and ASP(vbscript) are server side scripting languages that are used to pre process pages and output HTML before the page is sent to the visitor. HTML is the language that the browser understands that tells it how to display the page.
Client Side Operations
HTML is interpreted as it is read by the browser resulting in the display of the web page within the browser. Once the page has loaded HTML cannot be reprocessed without refreshing the page.
The relationship between server side and client side operations can be illustrated by the following example.
Suppose you wanted to display the current time on a web page. You have a number of options, you have the choice of displaying the current time according to the web server or the current time according to the visitors computer.
If you want to use the server time then server side pre processing will be required to determine the current time on the server and write it to the output in html format before the page is sent to the visitor.
This is not possible with server side scripting as the page needs to be re processed on the server to determine and output the new time and re send to the visitor in order for the new time to be displayed.
Whether you choose to display the local time on the server side or client side or any of the standard times such as GMT, PST, EST is irrelevant as both server and client operations use the respective local time and the time zone where the server or client is located to determine the time in the aforementioned standard times.