<?php
/////////////////////////////////////////////////////
// this class was build
// to handle session with cookie or not
// if you choose "zipcook" value the cookies
// are crypted and packed to hide data to malicious 
// users.
//
// $use_cookie parameter values:
// no --------> use session
// yes -------> use cookie, one cookie for each variable
// zipcook ---> encrypted cookies
//
// by Giulio Pons, http://www.barattalo.it
//
/////////////////////////////////////////////////////

class Session
{
	private $use_cookie;
	private $preStr;
	private $maxCookie;
	private $cookieLenght;
	private $stringone;
	private $duratacookie;
	private $secret;

	public function __construct ($cook = "zipcook") {

		$this->use_cookie = $cook;	//choose mode
		$this->preStr= "_KK_";		//prefix for cookies
		$this->maxCookie=20;		//since cookie lenght is limited, I've limited the number of cookies
		$this->cookieLenght=3096;	//max cookie length (it depends on browser)
		$this->duratacookie=3600*24;//cookie life time
		$this->secred="secret";		//secret keyword to crypt/decrypt, change this to customize encryption
		if ($this->use_cookie=="yes") {
		} elseif ($this->use_cookie=="zipcook") {
			$this->stringone = $this->prelevaStringaTotale();
		} else {
			ini_set("session.gc_maxlifetime","432000");
			ini_set("url_rewriter.tags","");
			ini_set("session.use_trans_sid", false);
			session_start();
		}
	}

	/* ------------------------------------------- */
	/* pack variables for parse_str                */
	/* ------------------------------------------- */
	private function build_str($ar) {
		$qs = array();
		foreach ($ar as $k => $v) { $qs[] = $k.'='.$v; }
		return join('&', $qs);
	}

	/* ------------------------------------------- */
	/* get the list of variables from the crypted  */
	/* cookies                                     */
	/* ------------------------------------------- */
	private function prelevaStringaTotale() {
		$cookiesSet = array_keys($_COOKIE);
		$out = "";
		for ($x=0;$x<count($cookiesSet);$x++) {
			if (strpos(" ".$cookiesSet[$x],$this->preStr)==1)
				$out.=$_COOKIE[$cookiesSet[$x]];
		}
		return $this->decrypta($out);
	}

	public function debug() {
		// for debug
		return $this->prelevaStringaTotale();
	}

	/* ------------------------------------------- */
	/* determine available cookies                 */
	/* ------------------------------------------- */
	private function calcolaCookieLiberi() {
		$cookiesSet = array_keys($_COOKIE);
		$c=0;
		for ($x=0;$x<count($cookiesSet);$x++) {
			if (strpos(" ".$cookiesSet[$x],$this->preStr)==1)
				$c+=1;
		}
		return $this->maxCookie - count($cookiesSet) + $c;
	}

	/* ------------------------------------------- */
	/* split the string in blocks to store cookies */
	/* ------------------------------------------- */
	private function my_str_split($s,$len) {
		$output = array();
		if (strlen($s)<=$len) {
			$output[0] = $s;
			return $output;
		}
		$i = 0;
		while (strlen($s)>0) {
			$s = substr($s,0,$len);
			$output[$i]=$s;
			$s = substr($s,$len);
			$i++;
		}
		return $output;
	}

	/* ------------------------------------------- */
	/* save vars in cookies or session             */
	/* ------------------------------------------- */
	public function register($var,$value) {
		$this->set($var,$value);
	}
	public function set($var,$value) {
		if ($this->use_cookie=="yes") {
			setcookie($var,$this->crypta($value),time()+$this->duratacookie,"/", $_SERVER['HTTP_HOST'] );
		} elseif ($this->use_cookie=="zipcook") {
			if ($this->stringone!="") {
				parse_str($this->stringone, $vars);
			} else {
				$vars=array();
			}
			$vars[$var] = $value;	//aggiungo-modifico valore
			$str = $this->crypta($this->build_str($vars));
			$arr = $this->my_str_split($str,$this->cookieLenght);
			$cLiberi = $this->calcolaCookieLiberi();
			if (count($arr) < $cLiberi) {
				// c'ho spazio, posso registrare
				$this->stringone = $this->build_str($vars);
				for ($i=0;$i<count($arr);$i++) {
					setcookie($this->preStr.$i,$arr[$i],time()+$this->duratacookie,"/", $_SERVER['HTTP_HOST'] );
				}
			} else {
				//cookie overflow
				return "errore cookie overflow";
			}
		} else {
			session_register($var);
		}
	}

	/* ------------------------------------------- */
	/* get variables back from cookies crypted or  */
	/* not, or directly from session               */
	/* ------------------------------------------- */
	public function get($var) {
		if ($this->use_cookie=="yes") {
			global $_COOKIE;
			return $this->decrypta($_COOKIE[$var]);
		} elseif ($this->use_cookie=="zipcook") {
			if ($this->stringone!="") {
				parse_str($this->stringone, $vars);
			} else {
				return "";
			}
			if(!isset($vars[$var])) {
				return "";
			}
			return $vars[$var];
		} else {
			if ($this->is_registered($var)) {
				$this->$var=$GLOBALS[$var];
			}
			else
				if(isset($GLOBALS[$var]))
					$this->$var = $GLOBALS[$var];
				else
						$this->$var="";
			return($this->$var);
		}
	}

	/* ------------------------------------------- */
	/* empty session or cookis                     */
	/* ------------------------------------------- */
	public function finish() {
		if ($this->use_cookie=="yes") {
			$cookiesSet = array_keys($_COOKIE);
			for ($x=0;$x<count($cookiesSet);$x++) {
				//echo $cookiesSet[$x]."<br/>";
				setcookie($cookiesSet[$x],"",time()-3600*24,"/", $_SERVER['HTTP_HOST'] );	//faccio scadere il cookie
			}

		} elseif ($this->use_cookie=="zipcook") {
			$cookiesSet = array_keys($_COOKIE);
			for ($x=0;$x<count($cookiesSet);$x++) {
				if (strpos(" ".$cookiesSet[$x],$this->preStr)==1)
					setcookie($cookiesSet[$x],"",time()-3600*24,"/",$_SERVER['HTTP_HOST']);
				$this->stringone="";
			}
		} else {
			session_destroy();
			$_SESSION = array();
		}
	}

	/* crypt */
	private function crypta($t){
		if ($t=="") return $t;
		$r = md5(10); $c=0; $v="";
		for ($i=0;$i<strlen($t);$i++){
			if ($c==strlen($r)) $c=0;
			$v.= substr($r,$c,1) . (substr($t,$i,1) ^ substr($r,$c,1));
			$c++;
		}
		return (base64_encode($this->ed($v)));
	}
	/* decrypt */
	private function decrypta($t) {
		if ($t=="") return $t;
		$t = $this->ed(base64_decode(($t)));
		$v = "";
		for ($i=0;$i<strlen($t);$i++){
			$md5 = substr($t,$i,1);
			$i++;
			$v.= (substr($t,$i,1) ^ $md5);
		}
		return $v;
	}

	/* used to crypt/decrypt */
	private function ed($t) {
		$r = md5($this->secret); $c=0; $v="";
		for ($i=0;$i<strlen($t);$i++) {
			if ($c==strlen($r)) $c=0;
			$v.= substr($t,$i,1) ^ substr($r,$c,1);
			$c++;
		}
		return $v;
	}


}
?>

http://www.barattalo.it/2009/12/21/php-session-class-with-crypted-cookies/

I’ve made this class that can use normal session variables, or cookies. This class can use cookies in two ways: store a single variable in each cookie, or pack many variables, encrypt, and store them into cookies.

Now I always use this class when I have to use session/cookies and when I know that I have not to put too many bytes in cookies (since cookie size is limited).

PHP Session class with encrypted cookies

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