Source for file Cache.class.php

<?php
/**
 * @package harmoni.utilities
 * 
 * @copyright Copyright &copy; 2005, Middlebury College
 * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License (GPL)
 *
 * @version $Id: Cache.class.php,v 1.3 2007/09/04 20:25:54 adamfranco Exp $
 */
 
define("CACHE_VARIABLE","__cache");
 
$_temp = CACHE_VARIABLE;
$$_temp = array();
unset($_temp);
 
/**
 * This class acts as a basic cache. It stores data in a multi-dimensional
 * associative array that is built at execution time to store any arbitrary data
 * by "filing".
 * @package harmoni.utilities
 * @copyright 2004
 * @version $Id: Cache.class.php,v 1.3 2007/09/04 20:25:54 adamfranco Exp $
 */
class Cache {
 
    function Cache() {
        die("<b>Cache is a static class - it should not be instantiated!</b>");
    }
    
    /**
     * Stores an object.
     * @param ref mixed $object Any variable that should be stored.
     * @param string $ident1 The first identifier for the object.
     * @param optional string $ident2,... Any number of additional identifiers.
     * @return void 
     * @access public
     */
    function store($object, $ident1) {
        $string = '';
        $displayParts = array();
        for ($i=1; $i<func_num_args(); $i++) {
            $part = func_get_arg($i);
            $string .= "['$part']";
            $displayParts[] = $part;
        }
        
        $cache =$GLOBALS[CACHE_VARIABLE];
        
        $eval = '$bool = isset($cache'.$string.');';
        eval($eval);
        if ($bool) {
            throwError( new Error(
                "Cache - an item with identifyer <b>".implode(":",$displayParts)."</b> is already stored!","Cache",true));
        }
        
        $eval = '$cache'.$string.' =$object;';
        eval($eval);
    }
 
    /**
     * Checks to see if we have any data stored under the given identifiers.
     * @param string $ident1 The first identifier for the object.
     * @param optional string $ident2,... Any number of additional identifiers.
     * @return boolean 
     * @access public
     */
    function contains($ident1) {
        $string = '';
        for ($i=0; $i<func_num_args(); $i++) {
            $part = func_get_arg($i);
            $string .= "['$part']";
            $displayParts[] = $part;
        }
        
        $cache =$GLOBALS[CACHE_VARIABLE];
        
        $eval = '$bool = isset($cache'.$string.');';
        eval($eval);
        return $bool;
    }
    
    /**
     * Retrieves stored data specified by the given identifiers.
     * @param string $ident1 The first identifier for the object.
     * @param optional string $ident2,... Any number of additional identifiers.
     * @return ref mixed
     * @access public
     */
    function get($ident1) {
        $string = '';
        for ($i=0; $i<func_num_args(); $i++) {
            $part = func_get_arg($i);
            $string .= "['$part']";
            $displayParts[] = $part;
        }
        
        $cache =$GLOBALS[CACHE_VARIABLE];
        
        $eval = '$bool = isset($cache'.$string.');';
        eval($eval);
        
        if (!$bool) {
            throwError( new Error(
                "Cache - no item with identifyer <b>".implode(":",$displayParts)."</b> is stored!","Cache",true));
        }
        
        $eval = '$object =$cache'.$string.';';
        eval($eval);
        return $object;
    }
    
}