Integer → String

IntString.php

<?php



/**

Usage:

require( TEMPLATEPATH . '/includes/Int_String.php' );
$intstr = new IntString;

echo $intstr->int2str( 123 ); // 123 → One Hundred and Twenty Three

**/



/**
 * Demo library class intended to be added to in the future
 */
class IntString {
    /***** NOTE: a const cannot be an array in PHP, so making these arrays static is the next best thing *****/

    /**
     * @var array $_numbersUnder20 Array containing the word associated with the index's number value
     */
    private static $_numbersUnder20 = [
        'zero', 'one', 'two', 'three', 'four',
        'five', 'six', 'seven', 'eight', 'nine',
        'ten', 'eleven', 'twelve', 'thirteen', 'fourteen',
        'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'
    ];

    /**
     * @var array $_tensDigits Array containing all tens digit values except 10
     */
    private static $_tensDigits = [
        'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'
    ];

    /**
     * @var array $_orderOfMagnitude Array containing the higher-order digit values; can also be
     *                               thought of as the order of magnitude of the target digit
     */
    private static $_orderOfMagnitude = [
        // Stopped at "quintillion" because the maximum PHP int value on 64-bit Linux is
        // 9,223,372,036,854,775,807 (a.k.a. 2^63 - 1 because PHP doesn't support unsigned ints)
        'thousand', 'million', 'billion', 'trillion', 'quadrillion', 'quintillion'
    ];


    /**
     * Recursively calculates the string-, word-based equivalent of the target integer
     *
     * @param integer $num Integer whose value will be converted to a word-based string
     * @param boolean $recursive Determines if the currently-executing code is being called
     *                           recursively; allows for non-recursive 0 to be converted to "zero"
     *                           otherwise use an empty string
     *
     * @throws InvalidArgumentException if the first argument is not of type int
     *
     * @return string Partially- or fully-built word-based representation of the target integer
     */
    private function _integerToWords($num, $recursive=false) {
        // Ensure a valid integer
        if(!is_int($num)) {
            throw new InvalidArgumentException(
                __FUNCTION__ . ' expects parameter 1 to be of type integer; actual type: ' .
                gettype($num)
            );
        }


        /***** Perform the int to string conversion based on the size of $num *****/

        // Negative
        if($num < 0) {
            return 'negative ' . $this->_integerToWords(-1 * $num, true);
        }

        // 0 or no value in the lowest digits
        if($num === 0) {
            return $recursive ? '' : 'zero';
        }

        // 1-19
        if($num < 20) {
            return self::$_numbersUnder20[$num];
        }

        // 20 - 99
        if($num < 100) {
            $highDigitValue = intval(floor($num / 10) - 2); // Value of the highest-order digit
            $remainingValue = $num % 10; // Value of the remaining digits
            return
                self::$_tensDigits[$highDigitValue] .
                '-' .
                $this->_integerToWords($remainingValue, true);
        }


        // 100 - 999
        if($num < 1000) {
            $highDigitValue = intval(floor($num / 100)); // Value of the highest-order digit
            $remainingValue = $num % 100; // Value of the remaining digits


            if( $remainingValue === 0 ) {
            	return
            		$this->_integerToWords($highDigitValue,true) .
            		'-hundred';
            } else {
	            return
	                $this->_integerToWords($highDigitValue, true) .
	                '-hundred and ' .
	                $this->_integerToWords($remainingValue, true);
            }
        }

        // 1,000+
        $quotient = $num;
        $divideCount = 0;
        while($quotient >= 1000) {
            $quotient /= 1000;
            ++$divideCount;
        }
        $highDigitValue = intval(floor($quotient)); // Value of the highest-order digit
        $remainingValue = $num - ($highDigitValue * pow(1000, $divideCount)); // Value of the remaining digits
        return
            $this->_integerToWords($highDigitValue, true) .
            '-' .
            self::$_orderOfMagnitude[$divideCount - 1] .
            ' ' .
            $this->_integerToWords($remainingValue, true);
    }


    /**
     * @api
     *
     * Calculates the string-, word-based equivalent of the target integer
     *
     * @param integer $num Integer whose value will be converted to a word-based string
     *
     * @return string Fully-built word-based representation of the target integer
     */
    public function int2str($num) {
        return trim($this->_integerToWords($num), "- \t\n\r\0\x0B");
    }
}