Array to XML

<?php

/*

<atom:entry xmlns:atom='http://www.w3.org/2005/Atom' xmlns:gd='http://schemas.google.com/g/2005'>
    <atom:category scheme='http://schemas.google.com/g/2005#kind' term='http://schemas.google.com/contact/2008#contact' />
    <gd:name>
        <gd:givenName>Elizabeth</gd:givenName>
        <gd:familyName>Bennet</gd:familyName>
        <gd:fullName>Elizabeth Bennet</gd:fullName>
    </gd:name>
    <atom:content type='text'>Notes</atom:content>
    <gd:email rel='http://schemas.google.com/g/2005#work' primary='true' address='liz@gmail.com' displayName='E. Bennet' />
    <gd:email rel='http://schemas.google.com/g/2005#home' address='liz@example.org' />
    <gd:phoneNumber rel='http://schemas.google.com/g/2005#work' primary='true'>
        (206)555-1212
    </gd:phoneNumber>
    <gd:phoneNumber rel='http://schemas.google.com/g/2005#home'>
        (206)555-1213
    </gd:phoneNumber>
    <gd:im address='liz@gmail.com' protocol='http://schemas.google.com/g/2005#GOOGLE_TALK' primary='true' rel='http://schemas.google.com/g/2005#home' />
    <gd:structuredPostalAddress rel='http://schemas.google.com/g/2005#work' primary='true'>
        <gd:city>Mountain View</gd:city>
        <gd:street>1600 Amphitheatre Pkwy</gd:street>
        <gd:region>CA</gd:region>
        <gd:postcode>94043</gd:postcode>
        <gd:country>United States</gd:country>
        <gd:formattedAddress>
            1600 Amphitheatre Pkwy Mountain View
        </gd:formattedAddress>
    </gd:structuredPostalAddress>
</atom:entry>

*/

$data = array(
    '_name' => 'atom:entry', // "_name" needs to be the first item in each element array
    '_attributes' => array(
        'xmlns:atom' => 'http://www.w3.org/2005/Atom',
        'xmlns:gd' => 'http://schemas.google.com/g/2005',
    ),
    array(
        '_name' => 'atom:category',
        '_attributes' => array(
            'scheme' => 'http://schemas.google.com/g/2005#kind',
            'term' => 'http://schemas.google.com/contact/2008#contact',
        ),
    ),
    array(
        '_name' => 'gd:name',
        array(
            '_name' => 'gd:givenName',
            '_value' => 'Elizabeth',
        ),
        array(
            '_name' => 'gd:familyName',
            '_value' => 'Bennet',
        ),
        array(
            '_name' => 'gd:fullName',
            '_value' => 'Elizabeth Bennet',
        ),
    ),
    array(
        '_name' => 'atom:content',
        '_attributes' => array(
            'type' => 'text',
        ),
        '_value' => 'Notes',
    ),
    array(
        '_name' => 'gd:email',
        '_attributes' => array(
            'rel' => 'http://schemas.google.com/g/2005#work',
            'primary' => 'true',
            'address' => 'liz@gmail.com',
            'displayName' => 'E. Bennet',
        ),
    ),
    array(
        '_name' => 'gd:email',
        '_attributes' => array(
            'rel' => 'http://schemas.google.com/g/2005#home',
            'address' => 'liz@example.org',
        ),
    ),
    array(
        '_name' => 'gd:phoneNumber',
        '_attributes' => array(
            'rel' => 'http://schemas.google.com/g/2005#work',
            'primary' => 'true',
        ),
        '_value' => '(206)555-1212',
    ),
    array(
        '_name' => 'gd:phoneNumber',
        '_attributes' => array(
            'rel' => 'http://schemas.google.com/g/2005#work',
        ),
        '_value' => '(206)555-1213',
    ),
    array(
        '_name' => 'gd:im',
        '_attributes' => array(
            'address' => 'liz@gmail.com',
            'protocol' => 'http://schemas.google.com/g/2005#GOOGLE_TALK',
            'primary' => 'true',
            'rel' => 'http://schemas.google.com/g/2005#home',
        ),
    ),
    array(
        '_name' => 'gd:structuredPostalAddress',
        '_attributes' => array(
            'rel' => 'http://schemas.google.com/g/2005#work',
            'primary' => 'true',
        ),
        array(
            '_name' => 'gd:city',
            '_value' => 'Mountain View',
        ),
        array(
            '_name' => 'gd:street',
            '_value' => '1600 Amphitheatre Pkwy',
        ),
        array(
            '_name' => 'gd:region',
            '_value' => 'CA',
        ),
        array(
            '_name' => 'gd:postcode',
            '_value' => '94043',
        ),
        array(
            '_name' => 'gd:country',
            '_value' => 'United States',
        ),
        array(
            '_name' => 'gd:formattedAddress',
            '_value' => '1600 Amphitheatre Pkwy Mountain View',
        ),
    ),
);


$dom = new DOMDocument();
$dom->formatOutput = true; // Pretty XML output

function generate_xml_element( $dom, $parent_element, $data ) {
    $element = null;

    foreach ( $data as $data_key => $data_value ) {

        // "_name" contains the name of the current element
        if ( '_name' === $data_key ) {
            $element_value = ( ! empty( $data['_value'] ) ) ? $data['_value'] : null;
            $element = $dom->createElement( $data_value, $element_value );
        }

        // "_attributes" contains the attributes of the current element
        elseif ( '_attributes' === $data_key && $element ) {
            foreach ( $data_value as $attribute_key => $attribute_value ) {
                $element->setAttribute( $attribute_key, $attribute_value );
            }
        }

        // If the key is numeric, then it's a child element
        elseif ( is_numeric( $data_key ) && $element ) {
            $element->appendChild( generate_xml_element( $dom, $element, $data_value ) );
        }

    }

    return $element;
}

$dom->appendChild( generate_xml_element( $dom, $dom, $data ) );

echo '<pre>' . htmlspecialchars( $dom->saveXML() );