A PHP Code block starts with "<?php" and ends with "?>", can be placed anywhere in the HTML.
On servers with shorthand enabled setting, you can start a code block with <? and end with ?>. But for compatibility, we recommend that you should always use the standard form "<?php" rather than the shorthand form.
<?php echo "Hello World" ?>
For PHP Code you should always ensure that it's ends with a semicolon ";" if your not using single line code for example.
<?php echo "Hello World"; ?>
Comments in PHP For comment in PHP You can use double front slash "//" OR you can use hash "#" for single line comment, and for commenting a block of code you can use "/*" "*/", for example.
<?php #This is single line comment and willl not excute on server. //This is also single line comment and willl not excute on server. /* Commenting a block of code for future reference */ echo "Hello World"; ?>