Chapter 14 XML

starsol · July 16th, 2003, 04:59 AM

I've been through the 'Lord of the Rings' themed example of how to get data from XML files, but I can't figure out how to get individual peices of data from an XML file.

For example, I have a US Dollars to Euros, Pounds, Canadian Dollars and Australian Dollars currency converter on several websites, and instead of having to manually edit the exchange rates in each file, I would prefer to edit just one XML file and have the exchange rates called from that.

The XML file I have created looks like:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE exchange_rates [
 <!ELEMENT currency (name, rate)>
 <!ELEMENT name (#PCDATA)>
 <!ELEMENT rate (#PCDATA)>
]>
<exchange_rates>
<currency nation="European Union">
 <name>Euro</name>
 <rate>0.890234</rate>
</currency>
<currency nation="United Kingdom">
 <name>Pound</name>
 <rate>0.625547</rate>
</currency>
<currency nation="Canada">
 <name>Canadian Dollar</name>
 <rate>1.3927</rate>
</currency>
<currency nation="Australia">
 <name>Australian Dollar</name>
 <rate>1.53421</rate>
</currency>
</exchange_rates>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

and the convertor file currently looks like this:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


[u]
Currency Converter





<?php
if( ! ($fp = fopen("http://www.starsol.co.uk/scripts/files/currency_ex.xml" , " r" )) )
 die("Unable to open XML file.");
$currency_counter = 0;
$currency_data = array();
$xml_current_tag_state ='';

function startElementHandler( $parser, $element_name , $element_attribs )
{
global $currency_counter;
global $currency_data;
global $xml_current_tag_state;

if( $element_name == "CURRENCY" )
{
$currency_data[$currency_counter]["nation"] = $element_attribs["NATION"];
}
else
{
$xml_current_tag_state = $element_name;
}
}

function endElementHandler( $parser, $element_name )
{
global $currency_counter;
global $currency_data;
global $xml_current_tag_state;

$xml_current_tag_state = '';

if( $element_name = "CURRENCY" )
{
$currency_counter++;
}
}
function characterDataHandler( $parser , $data )
{
global $currency_counter;
global $currency_data;
global $xml_current_tag_state;

if( $xml_current_tag_state == '' )
return;
if( $xml_current_tag_state == "NAME" ) {
$currency_data[$currency_counter]["name"] = $data;
}
if( $xml_current_tag_state == "RATE" ) {
$currency_data[$currency_counter]["rate"] = $data;
}
}
if( !($xml_parser = xml_parser_create()) )
die("Couldn't create XML parser.");

xml_set_element_handler($xml_parser, "startElementHandler", "endElementHandler");
xml_set_character_data_handler($xml_parser, "characterDataHandler");

while( $data = fread($fp, 4096) )
{
if( !xml_parse($xml_parser, $data, feof($fp)) )
{
break;
}
}
xml_parser_free($xml_parser);

for( $i=0 ; $i < $currency_counter ; ++$i )
{
echo $currency_data[$i]["name"];
echo $currency_data[$i]["rate"];
echo $currency_data[$i]["nation"];

if ($currency == "Euro"){
$convamount = $amount * $eurorate;
$convamount = round($convamount, 2);
echo"$amount US Dollars is approximately equal to $convamount Euros.";
}
if ($currency == "Pound"){
$convamount = $amount * $poundrate;
$convamount = round($convamount, 2);
echo"$amount US Dollars is approximately equal to $convamount Pounds.";
}
if ($currency == "Canadian Dollar"){
$convamount = $amount * $canadarate;
$convamount = round($convamount, 2);
echo"$amount US Dollars is approximately equal to $convamount Canadian Dollars.";
}
if ($currency == "Australian Dollar"){
$convamount = $amount * $ausrate;
$convamount = round($convamount, 2);
echo"$amount US Dollars is approximately equal to $convamount Australian Dollars.";
}
?>
 
Please note, that the exchange rates are updated manually, and may not be precisely accurate.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(The echos for $currency_data[$i]["name"]; and so on are just so I can check the calls are working.)

What I need to do is get the values for $eurorate, $poundrate, $canadarate and $ausrate from the XML file. I'm sure it's relatively simple, but I can't find anywhere that tells me where to do it.

Can anyone rescue me?

Thanks and best wishes,
Rupe

.

Rupe Parnell
www.starsol.co.uk

nikolai · July 16th, 2003, 01:52 PM

Well, the your problem is that you're unnecessarily obfuscating things by adding an array index ($i) that you don't need. If you would like to access currencies by their country, then the country itself should be the index into the array in which you store the currencies.

Here's your code, rewritten to reflect these changes:

Code:

<p align="center">
<b>[u]
Currency Converter
</u></b>
</p>

<p align="left">

<?php

function printr(&$var, $desc = '')
{
   echo '<pre>';
   if($desc != '') echo "$desc: ";
   print_r($var);
   echo "</pre>\n";
}

if(!($data = file_get_contents("currency_ex.xml")))
{
    die("Unable to open XML file.");
}

$curr_nation   = '';
$currency_data = array();
$tag_stack     = array();

function startElementHandler($parser, $name, $attrs)
{
    global $curr_nation;
    global $tag_stack;

    array_push($tag_stack, $name); // push onto the stack.

    if($name == "CURRENCY")
    {
        $curr_nation = $attrs["NATION"];
    }
}

function endElementHandler($parser, $element_name)
{
    global $tag_stack;
    array_pop($tag_stack);
}

function characterDataHandler($parser, $data)
{
    global $curr_nation;
    global $currency_data;
    global $tag_stack;

    $curr_tag = $tag_stack[count($tag_stack)-1];
    if($curr_tag == "NAME")
    {
        $currency_data[$curr_nation]["name"] = $data;
    }
    else if($curr_tag == "RATE")
    {
        $currency_data[$curr_nation]["rate"] = $data;
    }
}

if( !($xml_parser = xml_parser_create()) )
{
    die("Couldn't create XML parser.");
}

xml_set_element_handler($xml_parser, "startElementHandler", "endElementHandler");
xml_set_character_data_handler($xml_parser, "characterDataHandler");
xml_parse($xml_parser, $data, true);
xml_parser_free($xml_parser);

printr($currency_data, '$currency_data after parsing XML');

$amount = (isset($_GET['amount']))? $_GET['amount'] : 50;
foreach($currency_data as $nation => $data)
{
    echo "Country <i>$nation</i>. "
       . "Currency <i>$data[name]</i>. "
       . "Rate <i>$data[rate]</i>.\n";

    $convamount = round($amount * $data['rate'], 2);
    echo "<b>$amount</b> US Dollars is approximately equal to "
       . "<b>$convamount</b> {$data['name']}s.<br/>\n";
}
?>
<br><br>
<i>Please note, that the exchange rates are updated manually,
          and may not be precisely accurate.</i>

</p>

New -- I'm using file_get_contents() to read the file data, not messing with file pointers, fopen(), fread(), and feof().

Also -- I'm using a stack to keep track of which tag we're in, not a single string. I ditched your tag counter. I added a useful debugging function, printr(), to display the contents of the array after parsing.

I assume that $amount is 50, unless you pass in a new amount as a GET paramater.

Hope it helps!

Take care,

Nik
http://www.bigaction.org/

starsol · July 18th, 2003, 10:27 AM

Thanks Nik :) everything is working smoothly now.

Just a note to anyone reading this topic, the function file_get_contents requires PHP version 4.3.0 or higher.

There is a workaround in the note section for those running earlier versions on the official PHP website:
http://uk2.php.net/manual/en/functio...t-contents.php

Rupe Parnell
www.starsol.co.uk