$library = array(
    book => array(
        array(
            'authorFirst' => 'Mark'
            'authorLast' => 'Twain'
            'title' => 'The Innocents Abroad'
        ),
        array(
            'authorFirst' => 'Charles'
            'authorLast' => 'Dickens'
            'title' => 'Oliver Twist'
        )
    )
);

    
        
            Mark
            Twain
            
        
        
            Charles
            Dickens
            
        
    

class ArrayToXML
{
    /**
     * The main function for converting to an XML document.
     * Pass in a multi dimensional array and this recrusively loops through and builds up an XML document.
     *
     * @param array $data
     * @param string $rootNodeName - what you want the root node to be - defaultsto data.
     * @param SimpleXMLElement $xml - should only be used recursively
     * @return string XML
     */
    public static function toXml($data, $rootNodeName = 'data', &$xml=null)
    {
        // turn off compatibility mode as simple xml throws a wobbly if you don't.
        if (ini_get('zend.ze1_compatibility_mode') == 1)
        {
            ini_set ('zend.ze1_compatibility_mode', 0);
        }

        if (is_null($xml))
        {
            $xml = simplexml_load_string("");
        }

        // loop through the data passed in.
        foreach($data as $key => $value)
        {
            // if numeric key, assume array of rootNodeName elements
            if (is_numeric($key))
            {
                $key = $rootNodeName;
            }

            // delete any char not allowed in XML element names
            $key = preg_replace('/[^a-z0-9\-\_\.\:]/i', '', $key);

            // if there is another array found recrusively call this function
            if (is_array($value))
            {
                // create a new node unless this is an array of elements
                $node = ArrayToXML::isAssoc($value) ? $xml->addChild($key) : $xml;

                // recrusive call - pass $key as the new rootNodeName
                ArrayToXML::toXml($value, $key, $node);
            }
            else
            {
                // add single node.
                $value = htmlentities($value);
                $xml->addChild($key,$value);
            }

        }
        // pass back as string. or simple xml object if you want!
        return $xml->asXML();
    }

    // determine if a variable is an associative array
    public static function isAssoc( $array ) {
        return (is_array($array) && 0 !== count(array_diff_key($array, array_keys(array_keys($array)))));
    }
}

class ArrayToXML
{
	/**
	 * The main function for converting to an XML document.
	 * Pass in a multi dimensional array and this recrusively loops through and builds up an XML document.
	 *
	 * @param array $data
	 * @param string $rootNodeName - what you want the root node to be - defaultsto data.
	 * @param SimpleXMLElement $xml - should only be used recursively
	 * @return string XML
	 */
	public static function toXml($data, $rootNodeName = 'data', &$xml=null)
	{
		// turn off compatibility mode as simple xml throws a wobbly if you don't.
		if (ini_get('zend.ze1_compatibility_mode') == 1)
		{
			ini_set ('zend.ze1_compatibility_mode', 0);
		}
		
		if (is_null($xml))
		{
			$xml = simplexml_load_string("");
		}
		
		// loop through the data passed in.
		foreach($data as $key => $value)
		{
			// no numeric keys in our xml please!
			if (is_numeric($key))
			{
				// make string key...
				$key = "unknownNode_". (string) $key;
			}
			
			// delete any char not allowed in XML element names
			$key = preg_replace('/[^a-z0-9\-\_\.\:]/i', '', $key);
			
			// if there is another array found recrusively call this function
			if (is_array($value))
			{
				$node = $xml->addChild($key);
				// recrusive call.
				ArrayToXML::toXml($value, $rootNodeName, $node);
			}
			else 
			{
				// add single node.
                                $value = htmlentities($value);
				$xml->addChild($key,$value);
			}
			
		}
		// pass back as string. or simple xml object if you want!
		return $xml->asXML();
	}
}

` class ArrayToXML { /** * The main function for converting to an XML document. * Pass in a multi dimensional array and this recrusively loops through and builds up an XML document. * * @param array $data * @param string $rootNodeName - what you want the root node to be - defaultsto data. * @param SimpleXMLElement $xml - should only be used recursively * @return string XML */ public static function toXml($data, $rootNodeName = 'data', &$xml=null) { // turn off compatibility mode as simple xml throws a wobbly if you don't. if (iniget('zend.ze1compatibilitymode') == 1) { iniset ('zend.ze1compatibilitymode', 0); }

    if (is_null($xml))
    {
        $xml = simplexml_load_string("<$rootNodeName />");
    }

    // loop through the data passed in.
    foreach($data as $key => $value)
    {
        // no numeric keys in our xml please!
        if (is_numeric($key))
        {
            // make string key...
            $key = "unknownNode_". (string) $key;
        }

        // delete any char not allowed in XML element names
        $key = preg_replace('/[^a-z0-9\-\_\.\:]/i', '', $key);

        // if there is another array found recrusively call this function
        if (is_array($value))
        {
            $node = $xml->addChild($key);
            // recrusive call.
            ArrayToXML::toXml($value, $rootNodeName, $node);
        }
        else 
        {
            // add single node.
                            $value = htmlentities($value);
            $xml->addChild($key,$value);
        }

    }
    // pass back as string. or simple xml object if you want!
    return $xml->asXML();
}

} `

if(isnull($xml))
{
        $xml = simplexml_load_string("");
}