Differences between PHP / pHtml

.phtml was the standard file extension for PHP 2 programs. .php3 took over for PHP 3. When PHP 4 came out they switched to a straight .php. It's a huge facility developer-side, though, when your web project grows bigger.so using the .phtml extension rather than .php would just be a formality used to denote a file that is more html dense rather than php
You make use of both in this fashion:

• .PHP Page doesn't contain view-related code
• .PHTML Page contains little (if any) data logic and the most part of it is presentation-related