Generates Twiml using SimpleXmlElement.

Twiml.php

<?php
/**
 * Copyright 2011 Neuman Vong. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 */

class TwimlException extends Exception {}

/**
 * Twiml response XML generator.
 */
class Twiml {

	protected $element;

	/**
	 * Constructs a Twiml response.
	 *
	 * @param arg:
	 *   - SimpleXmlElement The element to wrap
	 *   - array An array of attributes to add to the element
	 *   - null Initialize an empty element named 'Response'
	 */
	public function __construct($arg = null) {
		switch (true) {
		case $arg instanceof SimpleXmlElement:
			$this->element = $arg;
			break;
		case $arg === null:
			$this->element = new SimpleXmlElement('<Response/>');
			break;
		case is_array($arg):
			$this->element = new SimpleXmlElement('<Response/>');
			foreach ($arg as $name => $value) {
				$this->element->addAttribute($name, $value);
			}
			break;
		default:
			throw new TwimlException('Invalid argument');
		}
	}

	/**
	 * Converts method calls into Twiml verbs.
	 *
	 * An basic example:
	 *
	 *     php> print $this->say('hello');
	 *     <Say>hello</Say>
	 *
	 * An example with attributes:
	 *
	 *     php> print $this->say('hello', array('voice' => 'woman'));
	 *     <Say voice="woman">hello</Say>
	 *
	 * You could even just pass in an attributes array, omitting the noun:
	 *
	 *     php> print $this->gather(array('timeout' => '20'));
	 *     <Gather timeout="20"/>
	 *
	 * @param verb string The Twiml verb.
	 * @param args array:
	 *   - (noun string)
	 *   - (noun string, attributes array)
	 *   - (attributes array)
	 */
	public function __call($verb, array $args) {
		list($noun, $attrs) = $args + array('', array());
		if (is_array($noun)) {
			list($attrs, $noun) = array($noun, '');
		}
		$child = empty($noun)
			? $this->element->addChild(ucfirst($verb))
			: $this->element->addChild(ucfirst($verb), $noun);
		foreach ($attrs as $name => $value) {
			$child->addAttribute($name, $value);
		}
		return new self($child);
	}

	/**
	 * Returns the object as XML.
	 */
	public function __toString() {
		return $this->element->asXml();
	}
}

TwimlTest.php

<?php

class TwimlTest extends PHPUnit_Framework_TestCase {
	function testStuff() {
		$r = new Twiml();
		$r->say('hello');
		$r->dial()->number('123', array('sendDigits' => '456'));
		$r->gather(array('timeout' => 15));

		$doc = simplexml_load_string($r);
		$this->assertEquals('Response', $doc->getName());
		$this->assertEquals('hello', (string)$doc->Say);
		$this->assertEquals('456', (string)$doc->Dial->Number['sendDigits']);
		$this->assertEquals('123', (string)$doc->Dial->Number);
		$this->assertEquals('15', (string)$doc->Gather['timeout']);
	}
}