gistfile1.php

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

	$uncountable = array('equipment', 'information', 'rice', 'money', 'species', '([^a-z]|mini|^)series', 'fish', 'sheep');

    $irregular = array(
    'person' => 'people',
    'man' => 'men',
    'child' => 'children',
    'sex' => 'sexes',
    'move' => 'moves');

    foreach ($uncountable as $_uncountable)
	{
        if(preg_match("/$_uncountable$/i", $word))
            return $word;
    }

    foreach ($irregular as $_plural=> $_singular)
	{
		$arr = array();
        if (preg_match('/('.$_singular.')$/i', $word, $arr))
            return preg_replace('/('.$_singular.')$/i', substr($arr[0],0,1).substr($_plural,1), $word);
    }

    foreach ($singular as $rule => $replacement)
	{
        if (preg_match($rule, $word))
            return preg_replace($rule, $replacement, $word);
    }

    return $word;
}
?>