Incorporating PHP Within HTML:
By default, the PHP document end with the extension.php. When a web server encounters this extension in a requested file, it automatically passes it to the PHP processor. Of course, the webserver is highly configurable, and some web developers choose to force files ending with .htm or .html to also get parsed by the PHP processor, usually, because they want to hide the fact that they are using PHP.
to trigger the PHP commands, you need to learn a new tag. Here is the first part:
<?php the first thing you may notice is that the tag has not been closed.this is because entire sections of PHP can be placed inside this tag,and they finish only when the closing part is encountered. ?>
for example: <? echo "Hello World"; ?>