PHP Server-Side or Client-Side ?

There are client-side methods and server-side methods to accomplish many tasks. When sending e-mail, for example, the client-side way is to open up the mail client software a preaddressed blank e-mail massage after the user clicks a MAILTO link. The server-side method is to make the user fill out a form, and the content are formatted as an email that  is sent via a simple Mail Transfer protocol (SMTP) server (which very well could be send machine that the server-side script is executing on). You can also choose between client method and server methods of browser-sniffing, from validation, drop-down lists, and arithmetic calculation, Sometimes you see subtle but meaningful differences in functionality (server-side drop-downs can be assembled dynamically, client-side cannot) but not always.
How to choose? know your audience. Server-side methods are generally a bit slower at runtime because of the extra transits they must make, but they don't assume anything about your visitor's browser capabilities and take less developer time to maintain.