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');
?>