How to Efficiently Iterate Multidimensional Arrays for XML Transformation?

Iterating Multidimensional Arrays for XML Transformation

Problem

Transforming multidimensional arrays into XML strings is a common task in data handling. Consider the following array:

$nodes = array(
    "parent node",
    "parent node",
    array(
        "child node",
        "child node",
        array(
            "grand child node",
            "grand child node"
        )
    )
);

The goal is to convert it into an XML string resembling the following structure:

<node>
    <node>parent node</node>
    <node>parent node</node>
    <node>
        <node>child node</node>
        <node>child node</node>
        <node>
            <node>grand child node</node>
            <node>grand child node</node>
        </node>
    </node>
</node>

Solution via Iteration

While recursive functions offer a viable approach, an iterative solution can be more efficient in some cases. Here's an example using an Iterator:

class TranformArrayIterator extends RecursiveIteratorIterator
{
    ... // Implementation omitted for brevity
}

This custom iterator allows for custom control over the iteration process, including:

• Indentation and depth tracking
• Starting and ending nodes
• Setting the current element as an XML node

To use the iterator:

$iterator = new TranformArrayIterator(new RecursiveArrayIterator($nodes));

foreach($iterator as $val) {
    echo $val;
}

Solution via XMLWriter

For greater control over XML generation, an XMLWriter can be used as a collaborator:

class TranformArrayIterator extends RecursiveIteratorIterator
{
    ... // Implementation omitted for brevity
}

$xmlWriter = new XmlWriter;
... // Configuration and initialization of XMLWriter omitted

$iterator = new TranformArrayIterator(
    $xmlWriter,
    new RecursiveArrayIterator($nodes)
);

In this scenario, the iterator has direct access to the XMLWriter, enabling fine-grained control over the generated XML structure.

Conclusion

Both iterative approaches provide efficient ways to transform multidimensional arrays into XML strings. The specific choice depends on the desired level of control over the XML output.

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