How to insert RDF content into a Web site in PHP (3)

}
}

Destroy parser
Xml_parser_free ($XP),

Opening Tag Handler
function Elementbegin ($parser, $name, $attributes)
{
Global $currentTag, $flag,
Export the name of the current tag to the global scope
$currentTag = $name,
If within an item block, set a flag
if ($name = = "ITEM")
{
$flag = 1,
}
}

Closing Tag Handler
function Elementend ($parser, $name)
{
Global $currentTag, $flag,
$currentTag = "",
If exiting an item blocks, print a line and reset the flag
if ($name = = "ITEM")
{
echo "$flag = 0,
}
}

Character Data Handler
function Characterdata ($parser, $data)
{
Global $currentTag, $flag,
If within an item block, print item data
if ($currentTag = = "TITLE" | | $currentTag = = "LINK" | |
$currentTag = =
"DESCRIPTION") && $flag = = 1)
{
echo "$currentTag: $data <br>",
}
}

?>
Can't you see? Don't worry, there will be an explanation later.

5) Capture Flag
The first thing to do with this script is to set some global variables:
XML file
$file = "FM-RELEASES.RDF",

Set up some variables for use by the parser
$currentTag = "",
$flag = "",
$currentTag variable save is the name of the element that the parser is currently working on-you'll soon see why you need it.
Because my ultimate goal is to display every single item (item) in the channel with a link. Also know when the parser exits the <channel></channel> block and when it enters the <item></item> part of the document. Besides, I'm using the SAX parser, which works in a sequential fashion, with no parser APIs available, and no way to know the depth and location of the document tree. So I had to invent a mechanism to do it myself--that's why the $flag variable was introduced.
$flag variable will be used to determine whether the parser is in the <channel> block or in the <item> block.
The next step is to initialize the SAX parser and start parsing the RSS document.
Create parser
$XP = Xml_parser_create (),

Set Element Handler
Xml_set_element_handler ($XP, "Elementbegin", "Elementend"),
Xml_set_character_data_handler ($XP, "Characterdata"),
Xml_parser_set_option ($xp, xml_option_case_folding, TRUE),

Read XML file
if (!) ( $fp = fopen ($file, "R"))
{
Die ("Could not read $file"),
}

Parse data
while ($xml = Fread ($fp, 4096))
{
if (!xml_parse ($XP, $xml, feof ($FP))
{
Die ("XML parser Error:".)
Xml_error_string (Xml_get_error_code ($XP)),
}
}

Destroy parser
Xml_parser_free ($XP),

The code is straightforward, and the annotations are clear enough. The Xml_parser_create () function creates a parser instance and assigns it to the handle $XP. The callback function is then created to handle open and closed tags, as well as character data between the two. Finally, the Xml_parse () function is combined with multiple fread () calls to read the RDF file and parse it.
In the document, the Open tag processor Elementbegin () is invoked each time an open tag is encountered.
Opening Tag Handler
function Elementbegin ($parser, $name, $attributes)
{
Global $currentTag, $flag,
Export the name of the current tag to the global scope
$currentTag = $name,
If within an item block, set a flag
if ($name = = "ITEM")
{
$flag = 1,
}
}

This function takes the name and property of the current tag as the argument. The tag name is assigned to the global variable $currenttag. If the opening mark is <item&gt, then the $flag variable is placed in 1.
Similarly, if a closed tag is encountered, the closed tag processor Elementend () is invoked.
Closing Tag Handler
function Elementend ($parser, $name)
{
Global $currentTag, $flag,
$currentTag = "",
If exiting an item blocks, print a line and reset the flag
if ($name = = "ITEM")
{
echo "$flag = 0,
}
}
The closed tag handler function also takes the tag name as its argument. If you encounter a closed tag for </item>, the value of the variable $flag is reset to 0 and the value of the variable $currenttag is emptied.
So, how do you handle the character data between tags? This is where we are interested. Say hello to the character Data Processor (Characterdata) first.
Character Data Handler
function Characterdata ($parser, $data)
{
Global $currentTag, $flag,
If within an item block, print item data
if ($currentTag = = "TITLE" | | $currentTag = = "LINK" | |
$currentTag = =
"DESCRIPTION") && $flag = = 1)
{
echo "$currentTag: $data <br>",
}
}

Now you can look at the parameters passed to this function, and you'll find that it only receives data between the open and closed tags, and doesn't know which tag the parser is currently working on. And this is the reason we introduced the global variable $currenttag from the beginning.
If the value of the $flag variable is 1, that is, if the parser is currently between <item></itme> blocks, then the element currently being processed, whether <title>,<link> or < Description&gt, the data is printed on the output device (where the output device is a Web browser), followed by a newline character <br> after the output of each element.
The entire RDF document is processed in this order, showing a certain output for each <item> tag found. You can look at the following running results:


6 Nesting Time (Nesting times)
The previous example is just for illustration of the problem. If you really want to insert RDF content into a Web site, you need to do something a little better. So the previous script has been improved to add something to simplify the task of formatting RDF data.
<basefont face= "Verdana" >
<body>

<table border= "0" cellspacing= "5" cellpadding= "5" >
<tr>
<td><b>new releases on Freshmeat.net today:</b></td>
</tr>

<?php
XML file
$file = "HTTP://WWW.FRESHMEAT.NET/BACKEND/FM-RELEASES.RDF",

Set up some variables for use by the parser
$currentTag = "",
$flag = "",
$count = 0,

This is a associative array of channel data with keys ("title")
"Link",
"description")
$channel = Array (),