PHP实现货币换算的方法

<?php
/*
* File: CurrencyConverter.php
* Author: Simon Jarvis
* Copyright: 2005 Simon Jarvis
* Date: 10/12/05
* Link: http://www.white-hat-web-design.co.uk/articles/php-currency-conversion.php
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details:
* http://www.gnu.org/licenses/gpl.html
*
*/
class CurrencyConverter {
   var $xml_file = "www.ecb.int/stats/eurofxref/eurofxref-daily.xml";
   var $mysql_host, $mysql_user, $mysql_pass, $mysql_db, $mysql_table;
   var $exchange_rates = array();
   //Load Currency Rates
   function CurrencyConverter($host,$user,$pass,$db,$tb) {
      $this->mysql_host = $host;
      $this->mysql_user = $user;
      $this->mysql_pass = $pass;
      $this->mysql_db = $db;
      $this->mysql_table = $tb;
      $this->checkLastUpdated();
      $conn = mysql_connect($this->mysql_host,$this->mysql_user,$this->mysql_pass);
      $rs = mysql_select_db($this->mysql_db,$conn);
      $sql = "SELECT * FROM ".$this->mysql_table;
      $rs =  mysql_query($sql,$conn);
      while($row = mysql_fetch_array($rs)) {
         $this->exchange_rates[$row['currency']] = $row['rate'];
      }
   }
   /* Perform the actual conversion, defaults to £1.00 GBP to USD */
   function convert($amount=1,$from="GBP",$to="USD",$decimals=2) {
      return(number_format(($amount/$this->exchange_rates[$from])*$this->exchange_rates[$to],$decimals));
   }
   /* Check to see how long since the data was last updated */
   function checkLastUpdated() {
      $conn = mysql_connect($this->mysql_host,$this->mysql_user,$this->mysql_pass);
      $rs = mysql_select_db($this->mysql_db,$conn);
      $sql = "SHOW TABLE STATUS FROM ".$this->mysql_db." LIKE '".$this->mysql_table."'";
      $rs =  mysql_query($sql,$conn);
      if(mysql_num_rows($rs) == 0 ) {
         $this->createTable();
      } else {
         $row = mysql_fetch_array($rs);
         if(time() > (strtotime($row["Update_time"])+(12*60*60)) ) {
            $this->downloadExchangeRates();
         }
      }
   }
   /* Download xml file, extract exchange rates and store values in database */
   function downloadExchangeRates() {
      $currency_domain = substr($this->xml_file,0,strpos($this->xml_file,"/"));
      $currency_file = substr($this->xml_file,strpos($this->xml_file,"/"));
      $fp = @fsockopen($currency_domain, 80, $errno, $errstr, 10);
      if($fp) {
         $out = "GET ".$currency_file." HTTP/1.1rn";
         $out .= "Host: ".$currency_domain."rn";
         $out .= "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8) Gecko/20051111 Firefox/1.5rn";
         $out .= "Connection: Closernrn";
         fwrite($fp, $out);
         while (!feof($fp)) {
            $buffer .= fgets($fp, 128);
         }
         fclose($fp);
         $pattern = "{<Cubes*currency='(w*)'s*rate='([d.]*)'/>}is";
         preg_match_all($pattern,$buffer,$xml_rates);
         array_shift($xml_rates);
         for($i=0;$i<count($xml_rates[0]);$i++) {
            $exchange_rate[$xml_rates[0][$i]] = $xml_rates[1][$i];
         }
         $conn = mysql_connect($this->mysql_host,$this->mysql_user,$this->mysql_pass);
         $rs = mysql_select_db($this->mysql_db,$conn);
         foreach($exchange_rate as $currency=>$rate) {
            if((is_numeric($rate)) && ($rate != 0)) {
               $sql = "SELECT * FROM ".$this->mysql_table." WHERE currency='".$currency."'";
               $rs =  mysql_query($sql,$conn) or die(mysql_error());
               if(mysql_num_rows($rs) > 0) {
                  $sql = "UPDATE ".$this->mysql_table." SET rate=".$rate." WHERE currency='".$currency."'";
               } else {
                  $sql = "INSERT INTO ".$this->mysql_table." VALUES('".$currency."',".$rate.")";
               }
               $rs =  mysql_query($sql,$conn) or die(mysql_error());
            }
         }
      }
   }
   /* Create the currency exchange table */
   function createTable() {
      $conn = mysql_connect($this->mysql_host,$this->mysql_user,$this->mysql_pass);
      $rs = mysql_select_db($this->mysql_db,$conn);
      $sql = "CREATE TABLE ".$this->mysql_table." ( currency char(3) NOT NULL default '', rate float NOT NULL default '0', PRIMARY KEY(currency) ) ENGINE=MyISAM";
      $rs =  mysql_query($sql,$conn) or die(mysql_error());
      $sql = "INSERT INTO ".$this->mysql_table." VALUES('EUR',1)";
      $rs =  mysql_query($sql,$conn) or die(mysql_error());
      $this->downloadExchangeRates();
   }
}
?>

<?php
   include('CurrencyConverter.php');
   $x = new CurrencyConverter('your_host','your_username','your_password','your_database_name','your_table_name');
   echo $x->convert(2.50,'GBP','USD');
?>