Class for some transformations on Strings

StringTransform.class.php

<?php

class StringTransform
{
    /**
     * This Method Converts a String to Title Case
     * Not context-aware and just for english.
     *
     * @param string $str
     * @param bool   $apStyle use AP-Style title case if true
     *                        otherwise MLA-based (default)
     * @return string
     */
    public static function titleCase($str, $apStyle = false) {
        $str = strtolower($str);

        // normalize quotes
        $str = strtr($str, array(
            "‘" => "'",
            "’" => "'",
            '“' => '"',
            '”' => '"'
        ));

        $exclude = 'the a an of by at on in so to for and or nor but yet';
        if (!$apStyle) $exclude .= ' as than from into like with within since until upon before after over under up down above near between beyond';
        $exclude = explode(' ', $exclude);

        $regex = "/(?<!\w)[\p{L}']+/u";

        // split subphrases
        $substr = preg_split('/(\s?[\(\)\/:!?.]\s?)/', $str, null, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);

        for ($i = 0; $i < count($substr); $i++) {
            preg_match_all($regex, $substr[$i], $matches, PREG_OFFSET_CAPTURE);

            foreach ($matches[0] as $match) {
                list($word, $offset) = $match;
                $isFirst = ($offset == 0);
                $isLast = ($offset == strlen(rtrim($substr[$i])) - strlen($word));

                // capitalize all words not included in $excluded,
                // except shortened words with quote (eg. 'til),
                // with the first and last word always getting capitalized
                if ((!in_array($word, $exclude) && $word[0] != "'") || ($isFirst || $isLast)) {
                    $word = ucfirst($word);
                }

                $substr[$i] = substr_replace($substr[$i], $word, $offset, strlen($word));
            }
        }

        return implode($substr);
    }

    /**
     * ThisMethodConvertsAStringToPascalCase
     *
     * @param string $str
     * @return string
     */
    public static function pascalCase($str) {
        return self::replaceWhitespace(ucwords($str));
    }

    /**
     * thisMethodConvertsAStringToCamelCase
     *
     * @param string $str
     * @return string
     */
    public static function camelCase($str) {
        return lcfirst(self::replaceWhitespace(ucwords($str)));
    }

    /**
     * this_method_converts_a_string_to_snake_case
     *
     * @param string $str
     * @return string
     */
    public static function snakeCase($str) {
        return self::replaceWhitespace(strtolower($str), '_');
    }

    /**
     * ThIs MeThOd CoNvErTs A sTrInG tO sTuDlYcApS
     * multibyte-safe
     *
     * @param string $str
     * @param bool   $upperOdd   uppercase odd character positions
     * @param bool   $whitespace if false, whitespaces will be removed
     * @return string
     */
    public static function mixedCase($str, $upperOdd = false, $whitespace = true) {
        if (!$whitespace) {
            $str = self::replaceWhitespace($str);
        }

        $letters = preg_split('//u', mb_strtolower($str), null, PREG_SPLIT_NO_EMPTY);

        $i = 0;
        foreach ($letters as &$letter) {
            // only act on letters, ignore whitespace and other chars
            if (preg_match('/\p{L}/u', $letter)) {
                if ($i % 2 === (int) $upperOdd) {
                    $letter = mb_strtoupper($letter);
                }

                $i++;
            }
        }

        $str = implode($letters);

        return $str;
    }

    /**
     * Th1s m3th0d c0nv3rts 4 str1ng t0 l33t
     * multibyte-safe
     *
     * @param string       $str
     * @param string|array $mapping 'simple', 'full' (for all leet numbers)
     *                              or associative array for custom mapping, in the form 'letter' => number
     * @return string
     */
    public static function leet($str, $mapping = 'simple') {
        $leetChars = array(
            'a' => 4,
            'e' => 3,
            'i' => 1,
            'o' => 0
        );

        if ($mapping == 'full') {
            $extended = array(
                'g' => 6,
                's' => 5,
                't' => 7
            );

            $leetChars = array_merge($leetChars, $extended);
        } elseif (is_array($mapping)) {
            $leetChars = $mapping;
        }

        $letters = str_split($str);

        foreach ($letters as &$letter) {
            if (array_key_exists(strtolower($letter), $leetChars)) {
                $letter = strtolower($letter);
                $letter = $leetChars[$letter];
            }
        }

        $str = implode($letters);

        return $str;
    }

    private static function replaceWhitespace($str, $separator = '') {
        return preg_replace('/\s+/', $separator, $str);
    }
}