It's also possible to convert an XML document into a PHP object instead of a nested set of arrays, simply by setting appropriate options for the unserializer. Consider the following example, which demonstrates how this may be done:


<?php
 
// include class file
include("Unserializer.php");
 
// tell the unserializer to create an object
$options = array("complexType" => "object");
 
// create object
$unserializer = &new XML_Unserializer($options);
 
// unserialize the document
$result = $unserializer->unserialize("library.xml", true);    
 
// dump the result
print_r($unserializer->getUnserializedData());
 
? >



Here's the output:


stdClass Object
(
    [book] => Array
        (
            [0] => stdClass Object
                (
                    [title] => The Adventures of Sherlock Holmes
                    [author] => Arthur Conan Doyle
                    [price] => 24.95
                )
 
            [1] => stdClass Object
                (
                    [title] => Life of Pi
                    [author] => Yann Martel
                    [price] => 7.99
                )
 
            [2] => stdClass Object
                (
                    [title] => Europe on a Shoestring
                    [author] => Lonely Planet
                    [price] => 16.99
                )
        )
)



In this format, you can use standard object notation to access (for example) the title of the last book. The notation


$obj->book[2]->title



would return

Europe on a Shoestring

* Employment Options

Now, while all this is fine and dandy, how about using all this new-found knowledge for something practical?

This next example does just that, demonstrating how the XML_Serializer class can be used to convert data stored in a MySQL database into an XML document, and write it to a file for later use. Here's the MySQL table I'll be using,


mysql> SELECT * FROM employees;
+-----+--------+--------+-----+-----+----------------+---------+
| id  | lname  | fname  | age | sex | department     | country |
+-----+--------+--------+-----+-----+----------------+---------+
|  54 | Doe    | John   |  27 | M   | Engineering    | US      |
| 127 | Jones  | Sue    |  31 | F   | Finance        | UK      |
| 113 | Woo    | David  |  26 | M   | Administration | CN      |
| 175 | Thomas | James  |  34 | M   | Finance        | US      |
| 168 | Kent   | Jane   |  29 | F   | Administration | US      |
|  12 | Kamath | Ravina |  35 | F   | Finance        | IN      |
+-----+--------+--------+-----+-----+----------------+---------+
6 rows in set (0.11 sec)



and here's what I want my target XML document to look like:


<?xml version="1.0"? >
<employees>
    <employee>
        <lname>Doe</lname>
        <fname>John</fname>
        <age>27</age>
        <sex>M</sex>
        <department>Engineering</department>
        <country>US</country>
    </employee>
    <employee>
        <lname>Jones</lname>
        <fname>Sue</fname>
        <age>31</age>
        <sex>F</sex>
        <department>Finance</department>
        <country>UK</country>
    </employee>
    <employee>
        <lname>Woo</lname>
        <fname>David</fname>
        <age>26</age>
        <sex>M</sex>
        <department>Administration</department>
        <country>CN</country>
    </employee>
    <employee>
        <lname>Thomas</lname>
        <fname>James</fname>
        <age>34</age>
        <sex>M</sex>
        <department>Finance</department>
        <country>US</country>
    </employee>
    <employee>
        <lname>Kent</lname>
        <fname>Jane</fname>
        <age>29</age>
        <sex>F</sex>
        <department>Administration</department>
        <country>US</country>
    </employee>
    <employee>
        <lname>Kamath</lname>
        <fname>Ravina</fname>
        <age>35</age>
        <sex>F</sex>
        <department>Finance</department>
        <country>IN</country>
    </employee>
</employees>



With XML_Serializer, accomplishing this is a matter of a few lines of code. Here they are:


<?php
 
// include class file
include("Serializer.php");
 
// set output filename
$filename = 'employees.xml';
 
// set options
$options = array( "addDecl" => true,
   "defaultTagName" => "employee",
   "indent" => "    ",
   "rootName" => "employees");
 
// create object
$serializer = new XML_Serializer($options);
 
// open connection to database
$connection = mysql_connect("localhost", "user", "secret") or die
("Unable to connect!");
 
// select database
mysql_select_db("db1") or die ("Unable to select database!");
 
// execute query
$query = "SELECT * FROM employees";
$result = mysql_query($query) or die ("Error in query: $query. " .
mysql_error());
 
// iterate through rows and print column data
while ($row = mysql_fetch_array($result))
{
 $xml[] = array ( "lname" => $row[1],
    "fname" => $row[2],
    "age" => $row[3],
    "sex" => $row[4],
    "department" => $row[5],
    "country" => $row[6]);
}
 
// close database connection
mysql_close($connection);
 
// perform serialization
$result = $serializer->serialize($xml);
 
// open file
if (!$handle = fopen($filename, 'w')) 
{ 
 print "Cannot open file ($filename)";
 exit;
}
 
// write XML to file
if (!fwrite($handle, $serializer->getSerializedData())) 
{
 print "Cannot write to file ($filename)";
 exit;
}
 
// close file    
fclose($handle);
 
? >



Pretty simple, once you know how it works. First, I've opened up a connection to the database and retrieved all the records from the table. Then I've instantiated a new document tree and iterated over the result set, adding a new set of nodes to the tree at each iteration. Finally, once all the rows have been processed, the dynamically generated tree is written to a file for later use.