From: https://github.com/yabba/phpAdsNew/blob/master/libraries/deliverycache/cache-sysvshm.inc.php

cache-sysvshm.inc.php

<?php // $Revision: 1.2 $

/************************************************************************/
/* phpAdsNew 2                                                          */
/* ===========                                                          */
/*                                                                      */
/* Copyright (c) 2000-2002 by the phpAdsNew developers                  */
/* For more information visit: http://www.phpadsnew.com                 */
/*                                                                      */
/* 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.       */
/************************************************************************/

// Set define to prevent duplicate include
define ('LIBVIEWCACHE_INCLUDED', true);


define ('phpAds_shmopID', 0x2328);
define ('phpAds_shmopIndexSize', 4096);
define ('phpAds_shmopSegmentSize', 65536);


function phpAds_cacheFetch ($name)
{
	// First read cache structure from shared memory
	$shm_id = shm_attach(phpAds_shmopID);
	
	if ($shm_id) {
		// Get the size of the structure
		$size = shm_get_var($shm_id, 1);
		$size = hexdec ($size);
		
		if ($size > 0) {
			// Read the structure
			$structure = shm_get_var ($shm_id, 1);
			shm_detach ($shm_id);
			
			if (isset($structure[$name])) {
				$seg_id = shm_attach(phpAds_shmopID + $structure[$name]);
				
				if ($seg_id) {
					// Get the size of the structure
					$cache_size = shm_get_var ($seg_id, 1);
					$cache_size = hexdec ($cache_size);
					$cache_data = shm_get_var ($seg_id, 0);
					shm_detach($seg_id);
					
					return ($cache_data);
				} else {
					return false;
                                }
			} else {
				return false;
                        }
		} else {
			shm_detach ($shm_id);
			return false;
		}
	} else {
		return false;
        }
}

function phpAds_cacheStore ($name, $cache)
{
	// First read cache structure from shared memory
	$struc_id = shm_attach(phpAds_shmopID,phpAds_shmopIndexSize, 0644);
	
	if ($struc_id) {
		// Get the size of the structure
		$size = shm_get_var ($struc_id, 1);
		$size = hexdec ($size);
		
		// Fetch the structure
		if ($size > 0) {
			$structure = shm_get_var ($struc_id, 0);
		} else {
			$structure = array();
		}
		
		
		// Get highest segment id
		$highest = 0;
		reset ($structure);
		while (list($k, $v) = each ($structure))
			if ($v > $highest) $highest = $v;
		
		// Get lowest unused segment id
		for ($i = 1; $i <= $highest + 1; $i++) {
			if (!in_array($i, $structure)) {
				$segment = $i;
				break;
			}
		}
		
		if (isset($structure[$name]))
			$delete = $structure[$name];
		else
			$delete = false;
		
		$seg_id = shm_attach(phpAds_shmopID + $segment, phpAds_shmopSegmentSize, 0644);
		
		if ($seg_id) {
			// Store data
			$seg_data = $cache;
			$seg_size = strlen($seg_data);
			$seg_size = sprintf ('%04X', $seg_size);
			
			shm_put_var($seg_id, 1, $seg_size);
			shm_put_var($seg_id, 0, $seg_data);
			shm_detach($seg_id);
			
			
			// Update structure
			$structure[$name] = $segment;
			
			// Store the structure
			$struc_data = $structure;
			$struc_size = strlen($struc_data);
			$struc_size = sprintf ('%04X', $struc_size);
			
			shm_put_var($struc_id, 1, $struc_size);
			shm_put_var($struc_id, 0, $struc_data);
			shm_detach($struc_id);
			
			
			// Delete old segment
			if ($delete) {
				$del_id = shm_attach(phpAds_shmopID + $delete);
				shm_remove($del_id);
				shm_detach($del_id);
			}
			return true;
		} else {
			shm_detach($struc_id);
			return false;
		}
	}
	else {
		return false;
	}
}


function phpAds_cacheDelete ($name = '')
{
	// First read cache structure from shared memory
	$struc_id = shm_attach(phpAds_shmopID, phpAds_shmopIndexSize, 0644);
	
	if ($struc_id) {
		// Get the size of the structure
		$size = @shm_get_var ($struc_id, 1);
		$size = hexdec ($size);
		
		// Fetch the structure
		if ($size > 0) {
			$structure = shm_get_var ($struc_id, 0);
			// $structure = unserialize($structure);
		} else {
			return false;
                }
		
		
		if ($name != '' && isset($structure[$name])) {
			$delete = $structure[$name];
			
			// Update structure
			unset($structure[$name]);
			
			// Store the structure
			$struc_data = $structure;
			$struc_size = strlen($struc_data);
			$struc_size = sprintf ('%04X', $struc_size);
			
			shm_put_var($struc_id, 1, $struc_size);
			shm_put_var($struc_id, 0, $struc_data);
			shm_detach($struc_id);
			
			// Delete old segment
			$del_id = shm_attach(phpAds_shmopID + $delete);
			shm_remove($del_id);
			shm_detach($del_id);
			
			return true;
		}
		
		if ($name == '') {
			while (list($k, $v) = each($structure)) {
				// Delete old segment
				$del_id = shm_attach(phpAds_shmopID + $v);
				shm_remove($del_id);
				shm_detach($del_id);
			}
			
			$structure = array();
			
			// Store the structure
			$struc_data = $structure;
			$struc_size = strlen($struc_data);
			$struc_size = sprintf ('%04X', $struc_size);
			
			shm_put_var($struc_id, 1, $struc_size);
			shm_put_var($struc_id, 0, $struc_data);
			shm_detach($struc_id);
			
			return true;
		}
	}
	
	return false;
}


function phpAds_cacheInfo ()
{
	// First read cache structure from shared memory
	$struc_id = shm_attach(phpAds_shmopID);
	if ($struc_id) {
		// Get the size of the structure
		$structure = @shm_get_var ($struc_id, 0);
		shm_detach($struc_id);
		
		$result = array();
		while (list($k, $v) = each($structure)) { 
			// attach to the current segment
			$info_id = shm_attach(phpAds_shmopID + $v);
			
			// Get the size of the structure
			$result[$k] = sizeof(shm_get_var ($info_id, 0));
			
                        // detach from this element
			shm_detach($info_id);
		}
		
		return $result;
	}
	
	return false;
}


?>