1. [代码]参考ROR中的单复数转换，写一个PHP的单复数转换类      

$inflector = new Inflector();

echo $inflector->pluralize('bus') . '<br />';
echo $inflector->singularize('buses') . '<br />';

2. [文件]     inflector.php 

<?php

class Inflector {
  private $plural      = array();
  private $singular    = array();
  private $irregular   = array();
  private $uncountable = array();

  public function __construct() {
    $this->_update_plural();
    $this->_update_singular();
    $this->_update_irregular();
    $this->_update_uncountable();
  }


  public function pluralize($word) {
    return $this->_apply_inflections($word, $this->plural);
  }

  public function singularize($word) {
    return $this->_apply_inflections($word, $this->singular);
  }

  private function _apply_inflections($word, $rules) {
    $result = $word;
    if (empty($result)) return $result;
    if (sizeof($this->uncountable) > 0) {
      foreach($this->uncountable as $u) {
        if (preg_match("#^{$u}$#", $result)) {
          return $result;
        }
      }
    }

    for($i = (sizeof($rules) - 1); $i >=0; $i--) {
      $rule = $rules[$i];
      if (preg_match($rule[0], $result)) {
        $result = preg_replace($rule[0], $rule[1], $result);
        break;
      }    
    }

    return $result;
  }

  private function _update_plural() {
    $this->_plural('/$/', 's');
    $this->_plural('/s$/i', 's');
    $this->_plural('/(ax|test)is$/i', '\1es');
    $this->_plural('/(octop|vir)us$/i', '\1i');
    $this->_plural('/(octop|vir)i$/i', '\1i');
    $this->_plural('/(alias|status)$/i', '\1es');
    $this->_plural('/(bu)s$/i', '\1ses');
    $this->_plural('/(buffal|tomat)o$/i', '\1oes');
    $this->_plural('/([ti])um$/i', '\1a');
    $this->_plural('/([ti])a$/i', '\1a');
    $this->_plural('/sis$/i', 'ses');
    $this->_plural('/(?:([^f])fe|([lr])f)$/i', '\1\2ves');
    $this->_plural('/(hive)$/i', '\1s');
    $this->_plural('/([^aeiouy]|qu)y$/i', '\1ies');
    $this->_plural('/(x|ch|ss|sh)$/i', '\1es');
    $this->_plural('/(matr|vert|ind)(?:ix|ex)$/i', '\1ices');
    $this->_plural('/(m|l)ouse$/i', '\1ice');
    $this->_plural('/(m|l)ice$/i', '\1ice');
    $this->_plural('/^(ox)$/i', '\1en');
    $this->_plural('/^(oxen)$/i', '\1');
    $this->_plural('/(quiz)$/i', '\1zes');
  }

  private function _update_singular() {
    $this->_singular('/s$/i', '');
    $this->_singular('/(n)ews$/i', '\1ews');
    $this->_singular('/([ti])a$/i', '\1um');
    $this->_singular('/((a)naly|(b)a|(d)iagno|(p)arenthe|(p)rogno|(s)ynop|(t)he)ses$/i', '\1\2sis');
    $this->_singular('/(^analy)ses$/i', '\1sis');
    $this->_singular('/([^f])ves$/i', '\1fe');
    $this->_singular('/(hive)s$/i', '\1');
    $this->_singular('/(tive)s$/i', '\1');
    $this->_singular('/([lr])ves$/i', '\1f');
    $this->_singular('/([^aeiouy]|qu)ies$/i', '\1y');
    $this->_singular('/(s)eries$/i', '\1eries');
    $this->_singular('/(m)ovies$/i', '\1ovie');
    $this->_singular('/(x|ch|ss|sh)es$/i', '\1');
    $this->_singular('/(m|l)ice$/i', '\1ouse');
    $this->_singular('/(bus)es$/i', '\1');
    $this->_singular('/(o)es$/i', '\1');
    $this->_singular('/(shoe)s$/i', '\1');
    $this->_singular('/(cris|ax|test)es$/i', '\1is');
    $this->_singular('/(octop|vir)i$/i', '\1us');
    $this->_singular('/(alias|status)es$/i', '\1');
    $this->_singular('/^(ox)en/i', '\1');
    $this->_singular('/(vert|ind)ices$/i', '\1ex');
    $this->_singular('/(matr)ices$/i', '\1ix');
    $this->_singular('/(quiz)zes$/i', '\1');
    $this->_singular('/(database)s$/i', '\1');
  }

  private function _update_irregular() {
    $this->_irregular('person', 'people');
    $this->_irregular('man', 'men');
    $this->_irregular('child', 'children');
    $this->_irregular('sex', 'sexes');
    $this->_irregular('move', 'moves');
    $this->_irregular('cow', 'kine');
    $this->_irregular('zombie', 'zombies');
  }

  private function _update_uncountable() {
    $this->_uncountable('equipment');
    $this->_uncountable('information');
    $this->_uncountable('rice');
    $this->_uncountable('money');
    $this->_uncountable('species');
    $this->_uncountable('series');
    $this->_uncountable('fish');
    $this->_uncountable('sheep');
    $this->_uncountable('jeans');
  }

  private function _plural($rule, $replacement) {
    if (is_string($rule)) unset($this->uncountable[$rule]);
    unset($this->uncountable[$replacement]);
    $this->plural[sizeof($this->plural)] = array($rule, $replacement);
  }

  private function _singular($rule, $replacement) {
    if (is_string($rule)) unset($this->uncountable[$rule]);
    unset($this->uncountable[$replacement]);
    $this->singular[sizeof($this->singular)] = array($rule, $replacement);
  }

  private function _irregular($singular, $plural) {
    unset($this->uncountable[$singular]);
    unset($this->uncountable[$plural]);
    if (strtoupper(substr($singular, 0, 1)) == strtoupper(substr($plural, 0, 1))) {
      $this->_plural('/(' . substr($singular, 0, 1) . ')' . substr($singular, 1) . '$/i', '\1' . substr($plural, 1));
      $this->_plural('/(' . substr($plural, 0, 1) . ')' . substr($plural, 1) . '$/i', '\1' . substr($plural, 1));
      $this->_singular('/(' . substr($plural, 0, 1) . ')' . substr($plural, 1) . '$/i', '\1' . substr($singular, 1));
    } else {
      $this->_plural('/' . strtoupper(substr($singular, 0, 1)) . '(?i)' . substr($singular, 1) . '$/', 
        strtoupper(substr($plural, 0, 1)) . substr($plural, 1));
      $this->_plural('/' . strtolower(substr($singular, 0, 1)) . '(?i)' . substr($singular, 1) . '$/', 
        strtolower(substr($plural, 0, 1)) . substr($plural, 1));
      $this->_plural('/' . strtoupper(substr($plural, 0, 1)) . '(?i)' . substr($plural, 1) . '$/', 
        strtoupper(substr($plural, 0, 1)) . substr($plural, 1));
      $this->_plural('/' . strtolower(substr($plural, 0, 1)) . '(?i)' . substr($plural, 1) . '$/', 
        strtolower(substr($plural, 0, 1)) . substr($plural, 1));

      $this->_singular('/' . strtoupper(substr($plural, 0, 1)) . '(?i)' . substr($plural, 1) . '$/', 
        strtoupper(substr($singular, 0, 1)) . substr($singular, 1));
      $this->_singular('/' . strtolower(substr($plural, 0, 1)) . '(?i)' . substr($plural, 1) . '$/', 
        strtolower(substr($singular, 0, 1)) . substr($singular, 1));
    }
  }

  private function _uncountable($word) {
    $this->uncountable[] = $word;
  }
}

/* End of file inflector.php */
/* Location: ./application/libraties/inflector.php */