FractionsToWords.php

<?php

/**
 * Fractions To Words
 *
 * Description:
 * Takes a fraction (ie, 1/2) and outputs english words (ie, one-half)
 *
 * Special thanks to @Lamped (http://www.codingforums.com/archive/index.php/t-180473.html)
 * for direction on converting numbers to ordinal words
 *
 * @author Cornell Campbell (cornellsteven@gmail.com)
 * @copyright Copyright 2012 Cornell Campbell
 */
class FractionsToWords {
    
    private static $fraction;
    private static $whole_number = FALSE;
    private static $numerator;
    private static $denominator;
    
    /**
     * Array of names large numbers
     * Source: Wikipedia (http://en.wikipedia.org/wiki/Names_of_large_numbers)
     *
     * @var array
     */
    private static $scale = array(
        '', 'thousand', 'million', 'billion', 'trillion', 'quadrillion', 
        'quintillion', 'sextillion', 'octillion', 'nonillion', 'decillion', 
        'undecillion', 'duodecillion', 'tredecillion', 'quattuordecillion', 
        'quindecillion', 'sexdecillion', 'septendecillion', 'octodecillion', 
        'noverndecillion', 'vigintillion'
    );
    
    /**
     * An array of cardinal numbers 0 - 19
     *
     * @var array
     */
    private static $cardinals = array(
        '', 'one', 'two', 'three', 'four', 'five', 'six', 'seven',
        'eight', 'nine', 'ten', 'eleven', 'twelve', 'thirteen', 'fourteen',
        'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen',
    );
    
    /**
     * An array of ordinal numbers 0 - 19
     *
     * @var array
     */
    private static $ordinals = array(
        '', 'first', 'second', 'third', 'fourth', 'fifth', 'sixth',
        'seventh', 'eighth', 'ninth', 'tenth', 'eleventh', 'twelfth',
        'thirteenth', 'fourteenth', 'fifteenth', 'sixteenth', 'seventeenth',
        'eighteenth', 'nineteenth'
    );
    
    /**
     * An array of cardinal numbers by tens: 20 - 90
     *
     * @var array
     */
    private static $tensCardinals = array(
        '', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 
        'eighty', 'ninety',
    );
    
    /**
     * An array of ordinal numbers by tens: 20th - 90th
     *
     * @var array
     */
    private static $tensOrdinals = array(
        '', '', 'twentieth', 'thirtieth', 'fortieth', 'fiftieth', 'sixtieth', 
        'seventieth', 'eightieth', 'ninetieth',
    );
    
    /**
     * Main function to convert a fraction to words
     *
     * @param string $fraction 
     * @return string
     */
    public static function convert($fraction) {
        self::$fraction = $fraction;
        
        // Clean up input
        $fraction = trim($fraction);
        $fraction = preg_replace('/\s+/', ' ', $fraction);
        
        // Get parts of fraction
        $parts = explode(' ', $fraction);
        
        if (FALSE == strpos(self::$fraction, '/') || count($parts) > 2) {
            // If this does not appear to be an actual fraction, 
            // just return the original input string
            return self::$fraction;
        } else if (count($parts) === 2) {
            self::$whole_number = $parts[0];
            $fraction = $parts[1];
        } else {
            $fraction = $parts[0];
        }
        
        self::$numerator   = reset(explode('/', $fraction));
        self::$denominator = end(explode('/', $fraction));
        
        // Convert numbers to words
        $whole_number = self::numberToCardinal(self::$whole_number);
        $numerator    = self::numberToCardinal(self::$numerator);
        
        if (self::$denominator == 2) {
            $denominator = ( self::$numerator > 1 ? 'halves' : 'half' );
        } else {
            $denominator = self::numberToOrdinal(self::$denominator);
        }
        
        $glue     = ( count(explode('-', $denominator)) < 2 ? '-' : ' ' );
        $fraction = $numerator . $glue . $denominator;
        $fraction = str_replace(' -', '-', $fraction);
        
        if (self::$numerator > 1 && self::$denominator != 2) {
            $fraction .= 's';
        }
        
        // Check for whole number
        if ($whole_number) {
            $fraction = $whole_number . ' and ' . $fraction;
        }
        
        return trim($fraction);
    }
    
    /**
     * Turns a number into an array containing sections of a number (as strings)
     *
     * For example, 1234567 would become:
     * ['001', '234', '567']
     *
     * @param mixed $number 
     * @return array
     */
    private static function floatToArray($number) {
        return str_split(str_pad($number, ceil(strlen($number) / 3) * 3, '0', STR_PAD_LEFT), 3);
    }
    
    /**
     * Converts a number into english words
     *
     * @param mixed $number
     * @return string
     */
    private static function numberToEnglish($number) {
        $hundreds = floor($number / 100);
        $tens     = ($number % 100);
        $pre      = ($hundreds ? self::$cardinals[$hundreds] . ' hundred' : '');
        
        if ($tens < 20) {
            $post = self::$cardinals[$tens];
        } else {
            $post = trim(self::$tensCardinals[floor($tens / 10)]);
            
            if ( ! empty(self::$cardinals[$tens % 10])) {
                $post .= '-' . self::$cardinals[$tens % 10];
            }
        }
        
        if ($pre && $post) {
            return trim("$pre $post");
        }
        
        return trim($pre . $post);
    }
    
    /**
     * Converts an number into a English cardinal words 
     *
     * @param mixed $number
     * @return string
     */
    private static function numberToCardinal($number) {
        if ($number === FALSE) {
            return FALSE;
        }
        
        $int = array_reverse(self::floatToArray($number));
        for ($i = count($int)-1; $i > -1; $i--) {
            $englishNumber = self::numberToEnglish($int[$i]);
            
            if ($englishNumber) {
                $english[] = $englishNumber . ' ' . self::$scale[$i];
            }
        }
        
        $post = array_pop($english);
        $pre  = implode(' ', $english);
        
        if ($pre && $post) {
            $cardinal = trim("$pre $post");
        } else {
            $cardinal = $pre . $post;
        }
        
        return trim($cardinal);
    }
    
    /**
     * Converts a number into English ordinal words
     *
     * @param mixed $number 
     * @return string
     */
    private static function numberToOrdinal($number) {
        return trim(self::cardinalToOrdinal(self::numberToCardinal($number)));
    }
    
    /**
     * Converts a English-words cardinal number into English ordinal words
     *
     * @param string $cardinal 
     * @return string
     */
    private static function cardinalToOrdinal($cardinal) {
        $cardinal = trim($cardinal);
        $words    = explode(' ', $cardinal);
        $last     = &$words[count($words)-1];
        
        if (FALSE !== strpos($last, '-')) {
            $last_two = explode('-', $last);
            $pre      = $last_two[0];
            $last     = $last_two[1];
        }
        
        if (in_array($last, self::$cardinals)) {
            $last = self::$ordinals[array_search($last, self::$cardinals)];
        } else if (in_array($last, self::$tensCardinals)) {
            $last = self::$tensOrdinals[array_search($last, self::$tensCardinals)];
        } else if (substr($last, -2) != 'th') {
            $last .= 'th';
        }
        
        if (isset($pre)) {
            $last = "$pre-$last";
        }
        
        if (count($words) > 1) {
            if (FALSE === strpos($words[count($words)-1], '-')) {
                $last = array_pop($words);
                $words[count($words)-1] = $words[count($words)-1] . '-' . $last;
            }
        }
        
        return trim(implode(' ', $words));
    }
    
}