<?php

/*
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SIMPLE PAGE CACHING ENGINE
Author: Manish Raj
Website: http://technoslab.blogspot.com
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Table structure for cache.pages
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CREATE TABLE `pages` (
`pagehash` varchar(32) DEFAULT NULL,
`page` blob,
`cachetime` bigint(21) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
------------------------------------------------------
Usage: 
------------------------------------------------------
<?php
require('./class.cache.php');
$cache = new cache('localhost','root','','cache',3306,20);
?>
------------------------------------------------------
*/

class cache
{
	private $dbhost, $dbuser, $dbpass, $dbname, $dbport ;
	private $lifespan = 60 ;
	private $dbhandle = null ;
	private $pagehash = '' ;
	private $page = '' ;
	private $save = false ;

	// Constructor
	function __construct( $dbhost, $dbuser, $dbpass, $dbname, $dbport = 3306, $lifespan = 60 )
	{
		$this->dbhost = $dbhost ;
		$this->dbuser = $dbuser ;
		$this->dbpass = $dbpass ;
		$this->dbname = $dbname ;
		$this->dbport = $dbport ;
		$this->lifespan = $lifespan ;
		$this->connect() ;
		$this->render() ;
	}

	// Connect to database
	function connect()
	{
		$this->dbhandle = @new mysqli( $this->dbhost, $this->dbuser, $this->dbpass, $this->dbname, $this->dbport ) ;
		if ( ! empty( $this->dbhandle->connect_error ) )
		{
			exit( 'MySQL connection error.' ) ;
		}
	}

	// Retrive current page's md5 hash
	function current()
	{
		return md5( implode( '', $_GET ) . implode( '', $_POST ) . $_SERVER['REQUEST_URI'] ) ;
	}

	function render()
	{
		$current = $this->current() ;
		$lifespan = $_SERVER['REQUEST_TIME'] - $this->lifespan ;
		$check = $this->dbhandle->query( 'SELECT page FROM `pages` WHERE pagehash = "' . $current . '" AND cachetime > ' . $lifespan ) ;
		if ( $check->num_rows == 1 )
		{
			$contents = $check->fetch_object() ;
			echo $contents->page ;
			$this->delete() ;
			exit ;
		}
		else
		{
			ob_start() ;
			$this->save = true ;
			$this->pagehash = $current ;
		}
	}

	// Save to database
	function save( $pagehash, $page )
	{
		$this->dbhandle->query( 'INSERT INTO `pages` (pagehash,page,cachetime) VALUES ("' . $pagehash . '","' . $this->dbhandle->escape_string( $page ) . '",' . $_SERVER['REQUEST_TIME'] . ')' ) ;
	}

	// Delete old cached pages
	function delete()
	{
		$lifespan = $_SERVER['REQUEST_TIME'] - $this->lifespan ;
		$this->dbhandle->query( 'DELETE FROM `pages` WHERE cachetime < ' . $lifespan ) ;
	}

	// Destructor
	function __destruct()
	{
		if ( $this->save == true )
		{
			$this->page = ob_get_contents() ;
			ob_end_clean() ;
			$this->save( $this->pagehash, $this->page ) ;
			echo $this->page ;

		}
		if ( $this->dbhandle != null )
		{
			$this->dbhandle->close() ;
		}
	}
}

?>