Programming | Rizwan Abbasi's Blog

{ستمبر 11, 2006} HTML Vs XHTML

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You can prepare yourself for XHTML by starting to write strict HTML.

How To Get Ready For XHTML

XHTML is the next generation of HTML, but it will of course take some time before browsers and other software products are ready for it.
In the meantime there are some important things you can do to prepare yourself for it. As you will learn from this tutorial, XHTML is not very different from HTML 4.01, so bringing your code up to 4.01 standards is a very good start. Our complete HTML 4.01 reference can help you with that.
In addition, you should start NOW to write your HTML code in lowercase letters, and NEVER make the bad habit of skipping end tags like the </p>.
Happy coding!

The Most Important Differences:

XHTML elements must be properly nested
XHTML documents must be well-formed
Tag names must be in lowercase
All XHTML elements must be closed

Elements Must Be Properly Nested

In HTML some elements can be improperly nested within each other like this:

<b><i>This text is bold and italic</b></i>

In XHTML all elements must be properly nested within each other like this:

<b><i>This text is bold and italic</i></b>

Note: A common mistake in nested lists, is to forget that the inside list must be within a li element, like this:

<ul>

  <li>Coffee</li>

  <li>Tea

    <ul>

      <li>Black tea</li>

      <li>Green tea</li>

    </ul>

  <li>Milk</li>

</ul>

This is correct:

<ul>

  <li>Coffee</li>

  <li>Tea

    <ul>

      <li>Black tea</li>

      <li>Green tea</li>

    </ul>

  </li>

  <li>Milk</li>

</ul>

Notice that we have inserted a </li> tag after the </ul> tag in the "correct" code example.

Documents Must Be Well-formed

All XHTML elements must be nested within the <html> root element. All other elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element. The basic document structure is:

<html>

<head> ... </head>

<body> ... </body>

</html>

Tag Names Must Be In Lower Case

This is because XHTML documents are XML applications. XML is case-sensitive. Tags like <br> and <BR> are interpreted as different tags.
This is wrong:

<BODY>

<P>This is a paragraph</P>

</BODY>

This is correct:

<body>

<p>This is a paragraph</p>

</body>

All XHTML Elements Must Be Closed

Non-empty elements must have an end tag.
This is wrong:

<p>This is a paragraph

<p>This is another paragraph

This is correct:

<p>This is a paragraph</p>

<p>This is another paragraph</p>

Empty Elements Must Also Be Closed

Empty elements must either have an end tag or the start tag must end with />.
This is wrong:

This is a break<br>

Here comes a horizontal rule:<hr>

Here's an image <img src="happy.gif" alt="Happy face">

This is correct:

This is a break<br />

Here comes a horizontal rule:<hr />

Here's an image <img src="happy.gif" alt="Happy face" />

IMPORTANT Compatibility Note:
To make your XHTML compatible with today’s browsers, you should add an extra space before the "/" symbol like this: <br />, and this: <hr />.

{ستمبر 10, 2006} XHTML Vs HTML

You can prepare yourself for XHTML by starting to write strict HTML.

How To Get Ready For XHTML
XHTML is the next generation of HTML, but it will of course take some time before browsers and other software products are ready for it.
In the meantime there are some important things you can do to prepare yourself for it. As you will learn from this tutorial, XHTML is not very different from HTML 4.01, so bringing your code up to 4.01 standards is a very good start. Our complete HTML 4.01 reference can help you with that.
In addition, you should start NOW to write your HTML code in lowercase letters, and NEVER make the bad habit of skipping end tags like the

.
Happy coding!

The Most Important Differences:
• XHTML elements must be properly nested
• XHTML documents must be well-formed
• Tag names must be in lowercase
• All XHTML elements must be closed

Elements Must Be Properly Nested
In HTML some elements can be improperly nested within each other like this:
This text is bold and italic In XHTML all elements must be properly nested within each other like this: This text is bold and italic
Note: A common mistake in nested lists, is to forget that the inside list must be within a li element, like this:

Coffee
Tea
- Black tea
- Green tea
Milk

This is correct:

Coffee
Tea
- Black tea
- Green tea
Milk

Notice that we have inserted a

tag after the

tag in the "correct” code example.

Documents Must Be Well-formed
All XHTML elements must be nested within the root element. All other elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element. The basic document structure is:

…
…

Tag Names Must Be In Lower Case
This is because XHTML documents are XML applications. XML is case-sensitive. Tags like
and
are interpreted as different tags.
This is wrong:

This is a paragraph

This is correct:

This is a paragraph

All XHTML Elements Must Be Closed
Non-empty elements must have an end tag.
This is wrong:

This is a paragraph

This is another paragraph
This is correct:

This is a paragraph

This is another paragraph

Empty Elements Must Also Be Closed
Empty elements must either have an end tag or the start tag must end with />.
This is wrong:
This is a break
Here comes a horizontal rule:

Here’s an image Happy face
This is correct:
This is a break

Here comes a horizontal rule:

Here’s an image Happy face

IMPORTANT Compatibility Note:
To make your XHTML compatible with today’s browsers, you should add an extra space before the "/” symbol like this:
, and this:

{مارچ 10, 2006} 3rd Lecture.

You cannot view the PHP source code by selecting "View source” in the browser – you will only see the output from the PHP file, which is plain HTML. This is because the scripts are executed on the server before the result is sent back to the browser.

Basic PHP Syntax

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.
Below, we have an example of a simple PHP script which sends the text "Hello World” to the browser:

A PHP scripting block always starts with and ends with ?>. A PHP scripting block can be placed anywhere in the document.
Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.
There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text "Hello World”.

Variables in PHP

All variables in PHP start with a $ sign symbol. Variables may contain strings, numbers, or arrays.
Below, the PHP script assigns the string "Hello World” to a variable called $txt:

$txt="Hello World";

echo $txt;

?>

To concatenate two or more variables together, use the dot (.) operator:

$txt1="Hello World";

$txt2="1234";

echo $txt1 . " " . $txt2 ;

?>

The output of the script above will be: "Hello World 1234”.

Comments in PHP

In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

//This is a comment

/*

This is

a comment

block

*/

?>