Best practices when generating XML web services data for PHP

Question

I'm currently using Fusioncharts Free in my project which requires XML to be in a specific format, both for the display of data and for the appearance of the chart.

I have a PHP file called webservice.php which has many similar repetitions of the below:

$address = $_SERVER['PHP_SELF'];

...

if ($address == 'webService.php/fcf/last5pricechanges/'){
//query MySQL DB and build up XML string in $output variable to output to browser
//building up each line of XML more or less line by line
}

The outputted XML may look like so:

<graph caption="Active Items - Grouped by Site" showNames="1" decimalPrecision="0" bgcolor="eeeeee">
<set name="xyz.co.uk" value="1"/>
<set name="abc.com" value="5"/>
</graph>

It's becoming a bit of a maintenance nightmare to update this code, yet afaik it wouldn't be possible to transfer data using a standard format - such as REST, as Fusioncharts requires specific XML properties. Are there better ways to handle the above? Can I improve the modularity and maintainability of my code easily?

Answer 1

I've got a couple of ideas you could consider.

#1
Using a template engine, like Smarty, would probably make this a little easier to maintain. It would at least get rid of the XML from your PHP code.

For example, you could create a template for the XML snippet you posted:

<?xml version="1.0" encoding="UTF-8" ?>
{foreach from=$graphs item=graph}
    <graph caption="{$graph.caption}" showNames="{$graph.show_names}" decimalPrecision="{$graph.decimal_precision}" bgcolor="{$graph.bg_color}">
    {foreach from=$graph.set item=set}
        <set name="{$set.name}" value="{$set.value}"/>
    {/foreach}
    </graph>
{/foreach}

And call it from PHP as

<?php
$address = $_SERVER['PHP_SELF'];

$smart = new Smarty();
$graphs = array();

if ($address == 'webService.php/fcf/last5pricechanges/')
{
    $graph_result = mysql_query("SELECT caption, show_names, decimal_precision, bg_color
                                 FROM graph WHERE something='something else'");
    while($graph_row = mysql_fetch_assoc($graph_result))
    {
        $graph_row;
        $set_result = mysql_query("SELECT name, value FROM set WHERE graph_id = {$graph_row['id']}");
        while($set_row = mysql_fetch_assoc($set_result))
        {
            $graph_row['sets'][] = $set_row;
        }
        $graphs[] = $graph_row;
    }
}

$smarty->assign('graphs', $graphs);
$smarty->display('graph_template.tpl');
?>

#2
You could create objects to help you manage the code. For example, to generate the same XML output as before, you could do:

<?php
class Graph
{
    protected $caption;
    protected $show_names;
    protected $decimal_precision;
    protected $bg_color;

    protected $sets;

    public function __construct($graph_id)
    {
        $graph_result = mysql_query("SELECT caption, show_names, decimal_precision_bg_color
                                 FROM graph WHERE something='something else'");
        while($graph_row = mysql_fetch_assoc($graph_result))
        {
            list($this->caption, $this->show_names, $this->decimal_precision, $this->bg_color) = $graph_result;
            $set_result = mysql_query("SELECT name, value FROM set WHERE graph_id = {$graph_row['id']}");
            while($set_row = mysql_fetch_assoc($set_result))
            {
                $this->sets[] = $set_row;
            }
        }
    }

    public function fetch_xml()
    {
        $output  = '<?' . 'xml version="1.0" encoding="UTF-8" ?' . '>';
        $output .= "<graph caption=\"{$this->caption}\" showNames=\"{$this->show_names}\" decimalPrecision=\"{$this->decimal_precision}\" bgcolor=\"{$this->bg_color}\">\n";
        foreach($this->sets as $set)
        {
            $output .= "<set name=\"{$set->name}\" value=\"{$set->value}\"/>\n";
        }
        $output .= "</graph>";
        return $output;
    }
}
?>

And call it in your main code like:

<?php
$address = $_SERVER['PHP_SELF'];
if ($address == 'webService.php/fcf/last5pricechanges/')
{
    $graph = new Graph(1);
    echo $graph->fetch_xml();
}
?>

#3
You could try using something like SimpleXML, but I doubt that would help much with the maintainability, as it would be just as verbose as the echo method

And #4
... nope, I'm all out :-) Hope that helps.