fGrammar.php

<?php
/**
 * Provides english word inflection, notation conversion, grammar helpers and internationlization support
 *
 * @copyright  Copyright (c) 2007-2011 Will Bond
 * @author     Will Bond [wb] <will@flourishlib.com>
 * @license    http://flourishlib.com/license
 *
 * @package    Flourish
 * @link       http://flourishlib.com/fGrammar
 *
 */
class fGrammar
{
	// The following constants allow for nice looking callbacks to static methods
	const addCamelUnderscoreRule    = 'fGrammar::addCamelUnderscoreRule';
	const addHumanizeRule           = 'fGrammar::addHumanizeRule';
	const addSingularPluralRule     = 'fGrammar::addSingularPluralRule';
	const camelize                  = 'fGrammar::camelize';
	const humanize                  = 'fGrammar::humanize';
	const inflectOnQuantity         = 'fGrammar::inflectOnQuantity';
	const joinArray                 = 'fGrammar::joinArray';
	const pluralize                 = 'fGrammar::pluralize';
	const registerJoinArrayCallback = 'fGrammar::registerJoinArrayCallback';
	const reset                     = 'fGrammar::reset';
	const singularize               = 'fGrammar::singularize';
	const stem                      = 'fGrammar::stem';
	const underscorize              = 'fGrammar::underscorize';


	/**
	 * Cache for plural <-> singular and underscore <-> camelcase
	 *
	 * @var array
	 */
	static private $cache = array(
		'camelize'     => array(0 => array(), 1 => array()),
		'humanize'     => array(),
		'pluralize'    => array(),
		'singularize'  => array(),
		'underscorize' => array()
	);

	/**
	 * Custom rules for camelizing a string
	 *
	 * @var array
	 */
	static private $camelize_rules = array();

	/**
	 * Custom rules for humanizing a string
	 *
	 * @var array
	 */
	static private $humanize_rules = array();

	/**
	 * The callback to replace ::joinArray()
	 *
	 * @var callback
	 */
	static private $join_array_callback = NULL;

	/**
	 * Rules for plural to singular inflection of nouns
	 *
	 * @var array
	 */
	static private $plural_to_singular_rules = array(
		'([ml])ice$'                   => '\1ouse',
		'(media|info(rmation)?|news)$' => '\1',
		'(q)uizzes$'                   => '\1uiz',
		'(c)hildren$'                  => '\1hild',
		'(p)eople$'                    => '\1erson',
		'(m)en$'                       => '\1an',
		'((?!sh).)oes$'                => '\1o',
		'((?<!o)[ieu]s|[ieuo]x)es$'    => '\1',
		'([cs]h)es$'                   => '\1',
		'(ss)es$'                      => '\1',
		'([aeo]l)ves$'                 => '\1f',
		'([^d]ea)ves$'                 => '\1f',
		'(ar)ves$'                     => '\1f',
		'([nlw]i)ves$'                 => '\1fe',
		'([aeiou]y)s$'                 => '\1',
		'([^aeiou])ies$'               => '\1y',
		'(la)ses$'                     => '\1s',
		'(.)s$'                        => '\1'
	);

	/**
	 * Rules for singular to plural inflection of nouns
	 *
	 * @var array
	 */
	static private $singular_to_plural_rules = array(
		'([ml])ouse$'                  => '\1ice',
		'(media|info(rmation)?|news)$' => '\1',
		'(phot|log|vide)o$'            => '\1os',
		'^(q)uiz$'                     => '\1uizzes',
		'(c)hild$'                     => '\1hildren',
		'(p)erson$'                    => '\1eople',
		'(m)an$'                       => '\1en',
		'([ieu]s|[ieuo]x)$'            => '\1es',
		'([cs]h)$'                     => '\1es',
		'(ss)$'                        => '\1es',
		'([aeo]l)f$'                   => '\1ves',
		'([^d]ea)f$'                   => '\1ves',
		'(ar)f$'                       => '\1ves',
		'([nlw]i)fe$'                  => '\1ves',
		'([aeiou]y)$'                  => '\1s',
		'([^aeiou])y$'                 => '\1ies',
		'([^o])o$'                     => '\1oes',
		's$'                           => 'ses',
		'(.)$'                         => '\1s'
	);

	/**
	 * Custom rules for underscorizing a string
	 *
	 * @var array
	 */
	static private $underscorize_rules = array();


	/**
	 * Adds a custom mapping of a non-humanized string to a humanized string for ::humanize()
	 *
	 * @param  string $non_humanized_string  The non-humanized string
	 * @param  string $humanized_string      The humanized string
	 * @return void
	 */
	static public function addHumanizeRule($non_humanized_string, $humanized_string)
	{
		self::$humanize_rules[$non_humanized_string] = $humanized_string;

		self::$cache['humanize'] = array();
	}


	/**
	 * Adds a custom `camelCase` to `underscore_notation` and `underscore_notation` to `camelCase` rule
	 *
	 * @param  string $camel_case           The lower `camelCase` version of the string
	 * @param  string $underscore_notation  The `underscore_notation` version of the string
	 * @return void
	 */
	static public function addCamelUnderscoreRule($camel_case, $underscore_notation)
	{
		$camel_case = strtolower($camel_case[0]) . substr($camel_case, 1);
		self::$underscorize_rules[$camel_case] = $underscore_notation;
		self::$camelize_rules[$underscore_notation] = $camel_case;

		self::$cache['camelize']     = array(0 => array(), 1 => array());
		self::$cache['underscorize'] = array();
	}


	/**
	 * Adds a custom singular to plural and plural to singular rule for ::pluralize() and ::singularize()
	 *
	 * @param  string $singular  The singular version of the noun
	 * @param  string $plural    The plural version of the noun
	 * @return void
	 */
	static public function addSingularPluralRule($singular, $plural)
	{
		self::$singular_to_plural_rules = array_merge(
			array(
				'^(' . preg_quote($singular[0], '#') . ')' . preg_quote(substr($singular, 1), '#') . '$' =>
					'\1' . strtr(substr($plural, 1), array('\\' => '\\\\', '$' => '\\$'))
			),
			self::$singular_to_plural_rules
		);
		self::$plural_to_singular_rules = array_merge(
			array(
				'^(' . preg_quote($plural[0], '#') . ')' . preg_quote(substr($plural, 1), '#') . '$' =>
					'\1' . strtr(substr($singular, 1), array('\\' => '\\\\', '$' => '\\$'))
			),
			self::$plural_to_singular_rules
		);

		self::$cache['pluralize']   = array();
		self::$cache['singularize'] = array();
	}


	/**
	 * Converts an `underscore_notation`, human-friendly or `camelCase` string to `camelCase`
	 *
	 * @param  string  $string  The string to convert
	 * @param  boolean $upper   If the camel case should be `UpperCamelCase`
	 * @return string  The converted string
	 */
	static public function camelize($string, $upper)
	{
		if (!strlen($string)) {
			throw new fProgrammerException(
				"An empty string was passed to %s",
				__CLASS__ . '::camelize()'
			);
		}

		$upper = (int)(bool) $upper;
		if (isset(self::$cache['camelize'][$upper][$string])) {
			return self::$cache['camelize'][$upper][$string];
		}

		$original = $string;

		// Handle custom rules
		if (isset(self::$camelize_rules[$string])) {
			$string = self::$camelize_rules[$string];
			if ($upper) {
				$string = ucfirst($string);
			}

		} else {
			// Make a humanized string like underscore notation
			if (strpos($string, ' ') !== FALSE) {
				$string = strtolower(preg_replace('#\s+#', '_', $string));
			}

			// Check to make sure this is not already camel case
			if (strpos($string, '_') === FALSE) {
				if ($upper) {
					$string = ucfirst($string);
				}

			// Handle underscore notation
			} else {
				$string[0] = strtolower($string[0]);
				if ($upper) {
					$string = ucfirst($string);
				}
				$string = preg_replace_callback('#_([a-z0-9])#i', array('self', 'camelizeCallback'), $string);
			}
		}

		self::$cache['camelize'][$upper][$original] = $string;
		return $string;
	}


	/**
	 * A callback used by ::camelize() to handle converting underscore to camelCase
	 *
	 * @param array $match  The regular expression match
	 * @return string  The value to replace the string with
	 */
	static private function camelizeCallback($match)
	{
		return strtoupper($match[1]);
	}


	/**
	 * Composes text using fText if loaded
	 *
	 * @param  string  $message    The message to compose
	 * @param  mixed   $component  A string or number to insert into the message
	 * @param  mixed   ...
	 * @return string  The composed and possible translated message
	 */
	static protected function compose($message)
	{
		$args = array_slice(func_get_args(), 1);

		if (class_exists('fText', FALSE)) {
			return call_user_func_array(
				array('fText', 'compose'),
				array($message, $args)
			);
		} else {
			return vsprintf($message, $args);
		}
	}


	/**
	 * Makes an `underscore_notation`, `camelCase`, or human-friendly string into a human-friendly string
	 *
	 * @param  string $string  The string to humanize
	 * @return string  The converted string
	 */
	static public function humanize($string)
	{
		if (!strlen($string)) {
			throw new fProgrammerException(
				"An empty string was passed to %s",
				__CLASS__ . '::humanize()'
			);
		}

		if (isset(self::$cache['humanize'][$string])) {
			return self::$cache['humanize'][$string];
		}

		$original = $string;

		if (isset(self::$humanize_rules[$string])) {
			$string = self::$humanize_rules[$string];

		// If there is no space, it isn't already humanized
		} elseif (strpos($string, ' ') === FALSE) {

			// If we don't have an underscore we probably have camelCase
			if (strpos($string, '_') === FALSE) {
				$string = self::underscorize($string);
			}

			$string = preg_replace_callback(
				'/(\b(api|css|gif|html|id|jpg|js|mp3|pdf|php|png|sql|swf|url|xhtml|xml)\b|\b\w)/',
				array('self', 'camelizeCallback'),
				str_replace('_', ' ', $string)
			);
		}

		self::$cache['humanize'][$original] = $string;

		return $string;
	}


	/**
	 * Returns the singular or plural form of the word or based on the quantity specified
	 *
	 * @param  mixed   $quantity                     The quantity (integer) or an array of objects to count
	 * @param  string  $singular_form                The string to be returned for when `$quantity = 1`
	 * @param  string  $plural_form                  The string to be returned for when `$quantity != 1`, use `%d` to place the quantity in the string
	 * @param  boolean $use_words_for_single_digits  If the numbers 0 to 9 should be written out as words
	 * @return string
	 */
	static public function inflectOnQuantity($quantity, $singular_form, $plural_form=NULL, $use_words_for_single_digits=FALSE)
	{
		if ($plural_form === NULL) {
			$plural_form = self::pluralize($singular_form);
		}

		if (is_array($quantity)) {
			$quantity = sizeof($quantity);
		}

		if ($quantity == 1) {
			return $singular_form;

		} else {
			$output = $plural_form;

			// Handle placement of the quantity into the output
			if (strpos($output, '%d') !== FALSE) {

				if ($use_words_for_single_digits && $quantity < 10) {
					static $replacements = array();
					if (!$replacements) {
						$replacements = array(
							0 => self::compose('zero'),
							1 => self::compose('one'),
							2 => self::compose('two'),
							3 => self::compose('three'),
							4 => self::compose('four'),
							5 => self::compose('five'),
							6 => self::compose('six'),
							7 => self::compose('seven'),
							8 => self::compose('eight'),
							9 => self::compose('nine')
						);
					}
					$quantity = $replacements[$quantity];
				}

				$output = str_replace('%d', $quantity, $output);
			}

			return $output;
		}
	}


	/**
	 * Returns the passed terms joined together using rule 2 from Strunk & White's 'The Elements of Style'
	 *
	 * @param  array  $strings  An array of strings to be joined together
	 * @param  string $type     The type of join to perform, `'and'` or `'or'`
	 * @return string  The terms joined together
	 */
	static public function joinArray($strings, $type)
	{
		$valid_types = array('and', 'or');
		if (!in_array($type, $valid_types)) {
			throw new fProgrammerException(
				'The type specified, %1$s, is invalid. Must be one of: %2$s.',
				$type,
				join(', ', $valid_types)
			);
		}

		if (self::$join_array_callback) {
			return call_user_func(self::$join_array_callback, $strings, $type);
		}

		settype($strings, 'array');
		$strings = array_values($strings);

		switch (sizeof($strings)) {
			case 0:
				return '';
				break;

			case 1:
				return $strings[0];
				break;

			case 2:
				return $strings[0] . ' ' . $type . ' ' . $strings[1];
				break;

			default:
				$last_string = array_pop($strings);
				return join(', ', $strings) . ' ' . $type . ' ' . $last_string;
				break;
		}
	}


	/**
	 * Returns the plural version of a singular noun
	 *
	 * @param  string  $singular_noun  The singular noun to pluralize
	 * @param  boolean $return_error   If this is `TRUE` and the noun can't be pluralized, `FALSE` will be returned instead
	 * @return string  The pluralized noun
	 */
	static public function pluralize($singular_noun, $return_error=FALSE)
	{
		if (!strlen($singular_noun)) {
			throw new fProgrammerException(
				"An empty string was passed to %s",
				__CLASS__ . '::pluralize()'
			);
		}

		if (isset(self::$cache['pluralize'][$singular_noun])) {
			return self::$cache['pluralize'][$singular_noun];
		}

		$original    = $singular_noun;
		$plural_noun = NULL;

		list ($beginning, $singular_noun) = self::splitLastWord($singular_noun);
		foreach (self::$singular_to_plural_rules as $from => $to) {
			if (preg_match('#' . $from . '#iD', $singular_noun)) {
				$plural_noun = $beginning . preg_replace('#' . $from . '#iD', $to, $singular_noun);
				break;
			}
		}

		if (!$plural_noun) {
			if ($return_error) {
				self::$cache['pluralize'][$singular_noun] = FALSE;
				return FALSE;
			}
			throw new fProgrammerException('The noun specified could not be pluralized');
		}

		self::$cache['pluralize'][$original] = $plural_noun;

		return $plural_noun;
	}


	/**
	 * Allows replacing the ::joinArray() function with a user defined function
	 *
	 * This would be most useful for changing ::joinArray() to work with
	 * languages other than English.
	 *
	 * @param  callback $callback  The function to replace ::joinArray() with - should accept the same parameters and return the same type
	 * @return void
	 */
	static public function registerJoinArrayCallback($callback)
	{
		if (is_string($callback) && strpos($callback, '::') !== FALSE) {
			$callback = explode('::', $callback);
		}
		self::$join_array_callback = $callback;
	}


	/**
	 * Resets the configuration of the class
	 *
	 * @internal
	 *
	 * @return void
	 */
	static public function reset()
	{
		self::$cache                    = array(
			'camelize'     => array(0 => array(), 1 => array()),
			'humanize'     => array(),
			'pluralize'    => array(),
			'singularize'  => array(),
			'underscorize' => array()
		);
		self::$camelize_rules           = array();
		self::$humanize_rules           = array();
		self::$join_array_callback      = NULL;
		self::$plural_to_singular_rules = array(
			'([ml])ice$'                   => '\1ouse',
			'(media|info(rmation)?|news)$' => '\1',
			'(q)uizzes$'                   => '\1uiz',
			'(c)hildren$'                  => '\1hild',
			'(p)eople$'                    => '\1erson',
			'(m)en$'                       => '\1an',
			'((?!sh).)oes$'                => '\1o',
			'((?<!o)[ieu]s|[ieuo]x)es$'    => '\1',
			'([cs]h)es$'                   => '\1',
			'(ss)es$'                      => '\1',
			'([aeo]l)ves$'                 => '\1f',
			'([^d]ea)ves$'                 => '\1f',
			'(ar)ves$'                     => '\1f',
			'([nlw]i)ves$'                 => '\1fe',
			'([aeiou]y)s$'                 => '\1',
			'([^aeiou])ies$'               => '\1y',
			'(la)ses$'                     => '\1s',
			'(.)s$'                        => '\1'
		);
		self::$singular_to_plural_rules = array(
			'([ml])ouse$'                  => '\1ice',
			'(media|info(rmation)?|news)$' => '\1',
			'(phot|log|vide)o$'            => '\1os',
			'^(q)uiz$'                     => '\1uizzes',
			'(c)hild$'                     => '\1hildren',
			'(p)erson$'                    => '\1eople',
			'(m)an$'                       => '\1en',
			'([ieu]s|[ieuo]x)$'            => '\1es',
			'([cs]h)$'                     => '\1es',
			'(ss)$'                        => '\1es',
			'([aeo]l)f$'                   => '\1ves',
			'([^d]ea)f$'                   => '\1ves',
			'(ar)f$'                       => '\1ves',
			'([nlw]i)fe$'                  => '\1ves',
			'([aeiou]y)$'                  => '\1s',
			'([^aeiou])y$'                 => '\1ies',
			'([^o])o$'                     => '\1oes',
			's$'                           => 'ses',
			'(.)$'                         => '\1s'
		);
	}


	/**
	 * Returns the singular version of a plural noun
	 *
	 * @param  string  $plural_noun   The plural noun to singularize
	 * @param  boolean $return_error  If this is `TRUE` and the noun can't be pluralized, `FALSE` will be returned instead
	 * @return string  The singularized noun
	 */
	static public function singularize($plural_noun, $return_error=FALSE)
	{
		if (!strlen($plural_noun)) {
			throw new fProgrammerException(
				"An empty string was passed to %s",
				__CLASS__ . '::singularize()'
			);
		}

		if (isset(self::$cache['singularize'][$plural_noun])) {
			return self::$cache['singularize'][$plural_noun];
		}

		$original      = $plural_noun;
		$singular_noun = NULL;

		list ($beginning, $plural_noun) = self::splitLastWord($plural_noun);
		foreach (self::$plural_to_singular_rules as $from => $to) {
			if (preg_match('#' . $from . '#iD', $plural_noun)) {
				$singular_noun = $beginning . preg_replace('#' . $from . '#iD', $to, $plural_noun);
				break;
			}
		}

		if (!$singular_noun) {
			if ($return_error) {
				self::$cache['singularize'][$plural_noun] = FALSE;
				return FALSE;
			}
			throw new fProgrammerException('The noun specified could not be singularized');
		}

		self::$cache['singularize'][$original] = $singular_noun;

		return $singular_noun;
	}


	/**
	 * Splits the last word off of a `camelCase` or `underscore_notation` string
	 *
	 * @param  string $string  The string to split the word from
	 * @return array  The first element is the beginning part of the string, the second element is the last word
	 */
	static private function splitLastWord($string)
	{
		// Handle strings with spaces in them
		if (strpos($string, ' ') !== FALSE) {
			return array(substr($string, 0, strrpos($string, ' ')+1), substr($string, strrpos($string, ' ')+1));
		}

		// Handle underscore notation
		if ($string == self::underscorize($string)) {
			if (strpos($string, '_') === FALSE) { return array('', $string); }
			return array(substr($string, 0, strrpos($string, '_')+1), substr($string, strrpos($string, '_')+1));
		}

		// Handle camel case
		if (preg_match('#(.*)((?<=[a-zA-Z_]|^)(?:[0-9]+|[A-Z][a-z]*)|(?<=[0-9A-Z_]|^)(?:[A-Z][a-z]*))$#D', $string, $match)) {
			return array($match[1], $match[2]);
		}

		return array('', $string);
	}


	/**
	 * Uses the Porter Stemming algorithm to create the stem of a word, which is useful for searching
	 *
	 * See http://tartarus.org/~martin/PorterStemmer/ for details about the
	 * algorithm.
	 *
	 * @param string $word  The word to get the stem of
	 * @return string  The stem of the word
	 */
	static public function stem($word)
	{
		$s_v  = '^([^aeiou][^aeiouy]*)?[aeiouy]';
		$mgr0 = $s_v . '[aeiou]*[^aeiou][^aeiouy]*';

		$s_v_regex  = '#' . $s_v . '#';
		$mgr0_regex = '#' . $mgr0 . '#';
		$meq1_regex = '#' . $mgr0 . '([aeiouy][aeiou]*)?$#';
		$mgr1_regex = '#' . $mgr0 . '[aeiouy][aeiou]*[^aeiou][^aeiouy]*#';

		$word = fUTF8::ascii($word);
		$word = strtolower($word);

		if (strlen($word) < 3) {
			return $word;
		}

		if ($word[0] == 'y') {
			$word = 'Y' . substr($word, 1);
		}

		// Step 1a
		$word = preg_replace('#^(.+?)(?:(ss|i)es|([^s])s)$#', '\1\2\3', $word);

		// Step 1b
		if (preg_match('#^(.+?)eed$#', $word, $match)) {
			if (preg_match($mgr0_regex, $match[1])) {
				$word = substr($word, 0, -1);
			}

		} elseif (preg_match('#^(.+?)(ed|ing)$#', $word, $match)) {
			if (preg_match($s_v_regex, $match[1])) {
				$word = $match[1];
				if (preg_match('#(at|bl|iz)$#', $word)) {
					$word .= 'e';
				} elseif (preg_match('#([^aeiouylsz])\1$#', $word)) {
					$word = substr($word, 0, -1);
				} elseif (preg_match('#^[^aeiou][^aeiouy]*[aeiouy][^aeiouwxy]$#', $word)) {
					$word .= 'e';
				}
			}
		}

		// Step 1c
		if (substr($word, -1) == 'y') {
			$stem = substr($word, 0, -1);
			if (preg_match($s_v_regex, $stem)) {
				$word = $stem . 'i';
			}
		}

		// Step 2
		if (preg_match('#^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$#', $word, $match)) {
			if (preg_match($mgr0_regex, $match[1])) {
				$word = $match[1] . strtr(
					$match[2],
					array(
						'ational' => 'ate',  'tional'  => 'tion', 'enci'    => 'ence',
						'anci'    => 'ance', 'izer'    => 'ize',  'bli'     => 'ble',
						'alli'    => 'al',   'entli'   => 'ent',  'eli'     => 'e',
						'ousli'   => 'ous',  'ization' => 'ize',  'ation'   => 'ate',
						'ator'    => 'ate',  'alism'   => 'al',   'iveness' => 'ive',
						'fulness' => 'ful',  'ousness' => 'ous',  'aliti'   => 'al',
						'iviti'   => 'ive',  'biliti'  => 'ble',  'logi'    => 'log'
					)
				);
			}
		}

		// Step 3
		if (preg_match('#^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$#', $word, $match)) {
			if (preg_match($mgr0_regex, $match[1])) {
				$word = $match[1] . strtr(
					$match[2],
					array(
						'icate' => 'ic', 'ative' => '', 'alize' => 'al', 'iciti' => 'ic',
						'ical'  => 'ic', 'ful'   => '', 'ness'  => ''
					)
				);
			}
		}

		// Step 4
		if (preg_match('#^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize|(?<=[st])ion)$#', $word, $match) && preg_match($mgr1_regex, $match[1])) {
			$word = $match[1];
		}

		// Step 5
		if (substr($word, -1) == 'e') {
			$stem = substr($word, 0, -1);
			if (preg_match($mgr1_regex, $stem)) {
				$word = $stem;
			} elseif (preg_match($meq1_regex, $stem) && !preg_match('#^[^aeiou][^aeiouy]*[aeiouy][^aeiouwxy]$#', $stem)) {
				$word = $stem;
			}
		}

		if (preg_match('#ll$#', $word) && preg_match($mgr1_regex, $word)) {
			$word = substr($word, 0, -1);
		}

		if ($word[0] == 'Y') {
			$word = 'y' . substr($word, 1);
		}

		return $word;
	}


	/**
	 * Converts a `camelCase`, human-friendly or `underscore_notation` string to `underscore_notation`
	 *
	 * @param  string $string  The string to convert
	 * @return string  The converted string
	 */
	static public function underscorize($string)
	{
		if (!strlen($string)) {
			throw new fProgrammerException(
				"An empty string was passed to %s",
				__CLASS__ . '::underscorize()'
			);
		}

		if (isset(self::$cache['underscorize'][$string])) {
			return self::$cache['underscorize'][$string];
		}

		$original = $string;
		$string = strtolower($string[0]) . substr($string, 1);

		// Handle custom rules
		if (isset(self::$underscorize_rules[$string])) {
			$string = self::$underscorize_rules[$string];

		// If the string is already underscore notation then leave it
		} elseif (strpos($string, '_') !== FALSE && strtolower($string) == $string) {

		// Allow humanized string to be passed in
		} elseif (strpos($string, ' ') !== FALSE) {
			$string = strtolower(preg_replace('#\s+#', '_', $string));

		} else {
			do {
				$old_string = $string;
				$string = preg_replace('/([a-zA-Z])([0-9])/', '\1_\2', $string);
				$string = preg_replace('/([a-z0-9A-Z])([A-Z])/', '\1_\2', $string);
			} while ($old_string != $string);

			$string = strtolower($string);
		}

		self::$cache['underscorize'][$original] = $string;

		return $string;
	}
}



/**
 * Copyright (c) 2007-2011 Will Bond <will@flourishlib.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */