PHP: PHP Hypertext Preprocessor

• PHP is a server side language and must be run on a web server, not on a text editor and web browser as we did with HTML 5, CSS, JavaScript/JQuery.
• Similar to with HTML, it is a good idea to create at least one file with the name "index.php" in a directory as these files are displayed by default even when a filename is not specified. For this reason the home page of a site usually has the name of index.html or index.php
• When writing PHP code, the code must be prefixed, i.e. start with <?php and end with ?>.
• HTML code can NOT be put inside PHP code (since one is server side code, and the other is browser side code).
• Unlike HTML, PHP code MUST end with a semi-colon ";"