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'); 
?>