| // | Co-authored by : CVH, Chris Hansel | // +----------------------------------------------------------------------+ // // $Id: UnitConvertor.php,v 1.00 2002/02/20 11:40:00 stasokhvat Exp $ /** * UnitConvertor is able to convert between different units and currencies. * * @author Stanislav Okhvat * @version $Id: UnitConvertor.php,v 1.00 2002/03/01 17:00:00 stasokhvat Exp $ * @package UnitConvertor * @access public * @history 01.03.2002 Implemented the code for regular and offset-based * conversions * * 13.12.2004 * By Chris Hansel (CVH): changed getConvSpecs in order to have it look up * intermediary conversions (also see comments in check_key). * * Intermediary conversions are useful when no conversion ratio is specified * between two units when we calculate between the two. For example, we want * to convert between Fahrenheit and Kelvin, and we have only * specified how to convert Centigrade<->Fahrenheit and * Centigrade<->Kelvin. While a direct (Fahrenheit->Kelvin) or * reverse (Kelvin->Fahrenheit) lookups fail, looking for an intermediary * unit linking the two (Centigrade) helps us do the conversion. * * 13.12.2004 * Chris Hansel (CVH): $to_array argument of addConversion method can now * contain units as 'unit1/unit2/unit3', when all units stand for the same * thing. See examples in unitconv.php */ class UnitConvertor { /** * Stores conversion ratios. * * @var array * @access private */ var $conversion_table = array(); /** * Decimal point character (default is "." - American - set in constructor). * * @var string * @access private */ var $decimal_point; /** * Thousands separator (default is "," - American - set in constructor). * * @var string * @access private */ var $thousand_separator; /** * For future use * * @var array * @access private */ var $bases = array(); /** * Constructor. Initializes the UnitConvertor object with the most important * properties. * * @param string decimal point character * @param string thousand separator character * @return void * @access public */ function UnitConvertor($dec_point = '.', $thousand_sep = ',') { $this->decimal_point = $dec_point; $this->thousand_separator = $thousand_sep; } // end func UnitConvertor /** * Adds a conversion ratio to the conversion table. * * @param string the name of unit from which to convert * @param array array( * "pound"=>array("ratio"=>'', "offset"=>'') * ) * "pound" - name of unit to set conversion ration to * "ratio" - 'double' conversion ratio which, when * multiplied by the number of $from_unit units produces * the result * "offset" - an offset from 0 which will be added to * the result when converting (needed for temperature * conversions and defaults to 0). * @return boolean true if successful, false otherwise * @access public */ function addConversion($from_unit, $to_array) { if (!isset($this->conversion_table[$from_unit])) { while(list($key, $val) = each($to_array)) { if (strstr($key, '/')) { $to_units = explode('/', $key); foreach ($to_units as $to_unit) { $this->bases[$from_unit][] = $to_unit; if (!is_array($val)) { $this->conversion_table[$from_unit."_".$to_unit] = array("ratio"=>$val, "offset"=>0); } else { $this->conversion_table[$from_unit."_".$to_unit] = array( "ratio"=>$val['ratio'], "offset"=>(isset($val['offset']) ? $val['offset'] : 0) ); } } } else { $this->bases[$from_unit][] = $key; if (!is_array($val)) { $this->conversion_table[$from_unit."_".$key] = array("ratio"=>$val, "offset"=>0); } else { $this->conversion_table[$from_unit."_".$key] = array( "ratio"=>$val['ratio'], "offset"=>(isset($val['offset']) ? $val['offset'] : 0) ); } } } return true; } return false; } // end func addConversion /** * Converts from one unit to another using specified precision. * * @param double value to convert * @param string name of the source unit from which to convert * @param string name of the target unit to which we are converting * @param integer double precision of the end result * @access public */ function convert($value, $from_unit, $to_unit, $precision) { if ($this->getConvSpecs($from_unit, $to_unit, $value, $converted )) { return number_format($converted , (int)$precision, $this->decimal_point, $this->thousand_separator); } else { return false; } } // end func /** * CVH : changed this Function getConvSpecs in order to have it look up * intermediary Conversions from the * "base" unit being that one that has the highest hierarchical order in one * "logical" Conversion_Array * when taking $conv->addConversion('km', * array('meter'=>1000, 'dmeter'=>10000, 'centimeter'=>100000, * 'millimeter'=>1000000, 'mile'=>0.62137, 'naut.mile'=>0.53996, * 'inch(es)/zoll'=>39370, 'ft/foot/feet'=>3280.8, 'yd/yard'=>1093.6)); * "km" would be the logical base unit for all units of dinstance, thus, * if the function fails to find a direct or reverse conversion in the table * it is only logical to suspect that if there is a chance * converting the value it only is via the "base" unit, and so * there is not even a need for a recursive search keeping the perfomance * acceptable and the ressource small... * * CVH check_key checks for a key in the Conversiontable and returns a value */ function check_key( $key) { if ( array_key_exists ($key,$this->conversion_table)) { if (! empty($this->conversion_table[$key])) { return $this->conversion_table[$key]; } } return false; } /** * Key function. Finds the conversion ratio and offset from one unit to another. * * @param string name of the source unit from which to convert * @param string name of the target unit to which we are converting * @param double conversion ratio found. Returned by reference. * @param double offset which needs to be added (or subtracted, if negative) * to the result to convert correctly. * For temperature or some scientific conversions, * i.e. Fahrenheit -> Celcius * @return boolean true if ratio and offset are found for the supplied * units, false otherwise * @access private */ function getConvSpecs($from_unit, $to_unit, $value, &$converted) { $key = $from_unit."_".$to_unit; $revkey = $to_unit."_".$from_unit; $found = false; if ($ct_arr = $this->check_key($key)) { // Conversion Specs found directly $ratio = (double)$ct_arr['ratio']; $offset = $ct_arr['offset']; $converted = (double)(($value * $ratio)+ $offset); return true; } // not found in direct order, try reverse order elseif ($ct_arr = $this->check_key($revkey)) { $ratio = (double)(1/$ct_arr['ratio']); $offset = -$ct_arr['offset']; $converted = (double)(($value + $offset) * $ratio); return true; } // not found test for intermediary conversion else { // return ratio = 1 if keyparts match if ($key == $revkey) { $ratio = 1; $offset = 0; $converted = $value; return true; } // otherwise search intermediary reset($this->conversion_table); while (list($convk, $i1_value) = each($this->conversion_table)) { // split the key into parts $keyparts = preg_split("/_/",$convk); // return ratio = 1 if keyparts match // Now test if either part matches the from or to unit if ($keyparts[1] == $to_unit && ($i2_value = $this->check_key($keyparts[0]."_".$from_unit))) { // an intermediary $keyparts[0] was found // now let us put things together intermediary 1 and 2 $converted = (double)(((($value - $i2_value['offset']) / $i2_value['ratio']) * $i1_value['ratio'])+ $i1_value['offset']); $found = true; } elseif ($keyparts[1] == $from_unit && ($i2_value = $this->check_key($keyparts[0]."_".$to_unit))) { // an intermediary $keyparts[0] was found // now let us put things together intermediary 2 and 1 $converted = (double)(((($value - $i1_value['offset']) / $i1_value['ratio']) + $i2_value['offset']) * $i2_value['ratio']); $found = true; } } return $found; } } // end func getConvSpecs } // end class UnitConvertor ?>