PHP generates XML simple example code

Use PHP DOMDocument to create dynamic XML files [Recommended reading: php introductory tutorial]

When dealing with XML-based applications, developers often need to establish XML-encoded data structures. For example, XML state templates in the Web based on user input, server request XML statements, and client responses based on runtime parameters.

Although the construction of XML data structure is time-consuming, if you use the mature PHP DOM application interface, everything will become simple and clear. This article will introduce you to the main functions of the PHP DOM application interface and demonstrate how to generate a correct complete XML file and save it to disk.

Create document type declaration

Generally speaking, XML declarations are placed at the top of the document. Declaration in PHP is very simple: just instantiate an object of the DOM document class and give it a version number. View Listing A:

Listing A

<?php
// create doctype
$dom = new DOMDocument（"1.0"）；
// display document in browser as plain text
// display document in browser as plain text
// for readability purposes
header（"Content-Type: text/plain"）；
// save and display tree
echo $dom->saveXML（）；
?>

Please note the saveXML() method of the DOM document object. I'll go into more detail about this method later, but for now you just need to briefly realize that it is used to output the current snapshot of the XML document to a file or browser. In this example, I've output the ASCII text directly to the browser to enhance readability. In practical applications, text/XML header files can be sent to the browser.

If you view the output in a browser, you can see the following code:

dc55d8f1b8d0d15e8e0c4fca7640a4b5

Add elements and text nodes

The real power of XML comes from its elements and The contents of the package. Fortunately, once you initialize the DOM document, many operations become very simple. This process includes the following two steps:

For each element or text node you want to add, call the createElement() or createTextNode() method of the DOM document object through the element name or text content. This creates a new object corresponding to the element or text node.

Add an element or text node to a parent node in the XML document tree by calling the node's appendChild() method and passing it the object created in the previous step.

The following example will clearly demonstrate these 2 steps, please see Listing B.

Program List B

<?php
// create doctype
$dom = new DOMDocument（"1.0"）；
// display document in browser as plain text
// for readability purposes
header（"Content-Type: text/plain"）；
// create root element
$root = $dom->createElement（"toppings"）；
$dom->appendChild（$root）；
// create child element
$item = $dom->createElement（"item"）；
$root->appendChild（$item）；
// create text node
$text = $dom->createTextNode（"pepperoni"）；
$item->appendChild（$text）；
// save and display tree
echo $dom->saveXML（）；
?>

Here, I first create a root element named 8bc7a580495bfabca110b6d1a58d0451 and place it in the XML header file. Then, I create an element named 5083cbefc9e5095dae6431462e2af988 and make it the root element. Finally, I create another text node with a value of "pepperoni" and assign it to the 5083cbefc9e5095dae6431462e2af988 element. The end result looks like this:

<?xml version="1.0"?>
<toppings>
<item>pepperoni</item>
</toppings>

If you want to add another topping, just create another 5083cbefc9e5095dae6431462e2af988 and add different content, as shown in Listing C.

Listing C

<?php
// create doctype
$dom = new DOMDocument（"1.0"）；
// display document in browser as plain text
// for readability purposes
header（"Content-Type: text/plain"）；
// create root element
$root = $dom->createElement（"toppings"）；
$dom->appendChild（$root）；
// create child element
$item = $dom->createElement（"item"）；
$root->appendChild（$item）；
// create text node
$text = $dom->createTextNode（"pepperoni"）；
$item->appendChild（$text）；
// create child element
$item = $dom->createElement（"item"）；
$root->appendChild（$item）；
// create another text node
$text = $dom->createTextNode（"tomato"）；
$item->appendChild（$text）；
// save and display tree
echo $dom->saveXML（）；
?>

The following is the output after executing Listing C:

<?xml version="1.0"?>
<toppings>
<item>pepperoni</item>
<item>tomato</item>
</toppings>

Adding attributes

By using attributes, you can also add appropriate information to elements. For the PHP DOM API, adding an attribute requires two steps: first create a node with the attribute name using the createAttribute() method of the DOM document object, and then add the document node to the attribute node with the attribute value. See Listing D for details.

Program Listing D

<?php
// create doctype
$dom = new DOMDocument（"1.0"）；
// display document in browser as plain text
// for readability purposes
header（"Content-Type: text/plain"）；
// create root element
$root = $dom->createElement（"toppings"）；
$dom->appendChild（$root）；
// create child element
$item = $dom->createElement（"item"）；
$root->appendChild（$item）；
// create text node
$text = $dom->createTextNode（"pepperoni"）；
$item->appendChild（$text）；
// create attribute node
$price = $dom->createAttribute（"price"）；
$item->appendChild（$price）；
// create attribute value node
$priceValue = $dom->createTextNode（"4"）；
$price->appendChild（$priceValue）；
// save and display tree
echo $dom->saveXML（）；
?>

The output looks like this:

<?xml version="1.0"?>
<toppings>
<item price="4">pepperoni</item>
</toppings>

Add CDATA module and process wizard

Although the CDATA module and process wizard are not often used, by calling the createCDATASection() and createProcessingInstruction() methods of the DOM document object, The PHP API also has good support for CDATA and process wizards, see Listing E.

Program Listing E

<?php
// create doctype
// create doctype
$dom = new DOMDocument（"1.0"）；
// display document in browser as plain text
// for readability purposes
header（"Content-Type: text/plain"）；
// create root element
$root = $dom->createElement（"toppings"）；
$dom->appendChild（$root）；
// create child element
$item = $dom->createElement（"item"）；
$root->appendChild（$item）；
// create text node
$text = $dom->createTextNode（"pepperoni"）；
$item->appendChild（$text）；
// create attribute node
$price = $dom->createAttribute（"price"）；
$item->appendChild（$price）；
// create attribute value node
$priceValue = $dom->createTextNode（"4"）；
$price->appendChild（$priceValue）；
// create CDATA section
$cdata = $dom->createCDATASection（" Customer requests that pizza be sliced into 16 square pieces "）；
$root->appendChild（$cdata）；
// create PI
$pi = $dom->createProcessingInstruction（"pizza", "bake（）"）；
$root->appendChild（$pi）；
// save and display tree
echo $dom->saveXML（）；
?>

The output looks like this:

<?xml version="1.0"?>
<toppings>
<item price="4">pepperoni</item>
<![CDATA[
Customer requests that pizza be sliced into 16 square pieces
]]>
<?pizza bake（）？>
</toppings>

Saving Results

Once you have achieved your goal, you can save the results in a file or store it in a variable in PHP. The results can be saved in a file by calling the save() method with a file name, or in a PHP variable by calling the saveXML() method. Please refer to the following example (Program List F):

Program List F

<?php
// create doctype
$dom = new DOMDocument（"1.0"）；
// create root element
$root = $dom->createElement（"toppings"）；
$dom->appendChild（$root）；
$dom->formatOutput=true;
// create child element
$item = $dom->createElement（"item"）；
$root->appendChild（$item）；
// create text node
$text = $dom->createTextNode（"pepperoni"）；
$item->appendChild（$text）；
// create attribute node
$price = $dom->createAttribute（"price"）；
$item->appendChild（$price）；
// create attribute value node
$priceValue = $dom->createTextNode（"4"）；
$price->appendChild（$priceValue）；
// create CDATA section
$cdata = $dom->createCDATASection（" Customer requests that pizza be
sliced into 16 square pieces "）；
$root->appendChild（$cdata）；
// create PI
$pi = $dom->createProcessingInstruction（"pizza", "bake（）"）；
$root->appendChild（$pi）；
// save tree to file
$dom->save（"order.xml"）；
// save tree to string
$order = $dom->save（"order.xml"）；
?>

The following is a practical example, you can test it.

xml.php（生成xml）
<?
$conn = mysql_connect（&#39;localhost&#39;, &#39;root&#39;, &#39;123456&#39;） or die（&#39;Could not connect: &#39; . mysql_error（））；
mysql_select_db（&#39;vdigital&#39;, $conn） or die （&#39;Can\&#39;t use database : &#39; . mysql_error（））；
$str = "SELECT id,username FROM `admin` GROUP BY `id` ORDER BY `id` ASC";
$result = mysql_query（$str） or die（"Invalid query: " . mysql_error（））；
if（$result）
{
$xmlDoc = new DOMDocument（）；
if（！file_exists（"01.xml"））{
$xmlstr = "<?xml version=&#39;1.0&#39; encoding=&#39;utf-8&#39; ?><message></message>";
$xmlDoc->loadXML（$xmlstr）；
$xmlDoc->save（"01.xml"）；
}
else { $xmlDoc->load（"01.xml"）；}
$Root = $xmlDoc->documentElement;
while （$arr = mysql_fetch_array（$result））{
$node1 = $xmlDoc->createElement（"id"）；
$text = $xmlDoc->createTextNode（iconv（"GB2312","UTF-8",$arr["id"]））；
$node1->appendChild（$text）；
$node2 = $xmlDoc->createElement（"name"）；
$text2 = $xmlDoc->createTextNode（iconv（"GB2312","UTF-8",$arr["username"]））；
$node2->appendChild（$text2）；
$Root->appendChild（$node1）；
$Root->appendChild（$node2）；
$xmlDoc->save（"01.xml"）；
}
}
mysql_close（$conn）；
?>

test.php (application test)

<?
$xmlDoc = new DOMDocument（）；
$xmlDoc->load（"http://localhost/xml/xml.php"）；
$x=$xmlDoc->getElementsByTagName（&#39;name&#39;）；
for （$i=0; $i<=$x->length-1; $i++）
{
if（strpos（$x->item（$i）->nodeValue,"fang"）！==false）
{
echo $x->item（$i）->parentNode->childNodes->item（1）->nodeValue;
}
}
?>