File Extensions:
Files including PHP code must end with extensions .php or .phtml
to be recognized form the web server.
Tags:
PHP script tags are "<?php" to open a PHP region and "?>" to close it
(or "<?" and "?>",
if short_open_tag is set in the PHP configuration file
or <% and %> for Active Server Pages, ASP).
Anything in between these tags is considered to be PHP code.
Expressions:
Expressions end with a semicolon ; .
They may contain line breaks.
Comments:
PHP supports 'C', 'C++' and Unix shell-style comments:
// and # comments the rest of a line and /* and */ comment
the inclosed region.
Variables:
Variables start with a dollar sign $.
The variable name is case-sensitive, they
must start with a letter or underscore.
Strings:
Strings are inclosed in quotation marks: "string".
The backslash \ keeps the next character from being
interpreted.
PHP info:
You can use the phpinfo() function to get information
about the PHP installation and state, etc: