Canonical PHP tags

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;
 # Second Example
print "This spans
multiple lines. The newlines will be
output as well";
?>

Multi-lines comments: They are generally used to provide pseudocode algorithms and more detailed explanations when necessary. The multiline style of commenting is the same as in C. Here are the example of multi lines comments.

<?
 /* This is a comment with multiline
Author : Mohammad Mohtashim
Purpose: Multiline Comments Demo
Subject: PHP
*/
 print "An example with multi line comments";