PHP Syntax Overview
This chapter will give you an idea of very basic syntax of PHP and very important to make your PHP foundation strong.
Escaping to PHP
The PHP parsing engine needs a way to differentiate PHP code from other elements in the page. The mechanism for doing so is known as 'escaping to PHP'. There are four ways to do this −
Canonical PHP tags
The most universally effective PHP tag style is −
<?php...?>

If you use this style, you can be positive that your tags will always be correctly interpreted.

Short-open (SGML-style) tags

Short or short-open tags look like this −

<?...?>

Short tags are, as one might expect, the shortest option You must do one of two things to enable PHP to recognize the tags −

·        Choose the --enable-short-tags configuration option when you're building PHP.

·        Set the short_open_tag setting in your php.ini file to on. This option must be disabled to parse XML with PHP because the same syntax is used for XML tags.

ASP-style tags

ASP-style tags mimic the tags used by Active Server Pages to delineate code blocks. ASP-style tags look like this −

<%...%>

To use ASP-style tags, you will need to set the configuration option in your php.ini file.

HTML script tags

HTML script tags look like this −

<script language="PHP">...</script>

Commenting PHP Code

A comment is the portion of a program that exists only for the human reader and stripped out before displaying the programs result. There are two commenting formats in PHP −

Single-line comments − They are generally used for short explanations or notes relevant to the local code. Here are the examples of single line comments.

<?

   # This is a comment, and

   # This is the second line of the comment

 


   // This is a comment too. Each style comments only

   print "An example with single line comments";

?>

Multi-lines printing − Here are the examples to print multiple lines in a single print statement −

<?

   # First Example

   print <<<END

   This uses the "here document" syntax to output

   multiple lines with $variable interpolation. Note

   that the here document terminator must appear on a

   line with just a semicolon no extra whitespace!

   END;