Parameter Passing & Session Tracking in PHP

Passing parameters & Session Tracking in PHP Prof. Ami Tusharkant Choksi Assistant Professor, Computer Engg. Dept., C.K.Pithawalla College of Engg. & Tech., Surat, Gujarat State, India.

What is Parameter Passing & Session Tracking? -> Values of the text typed in user form is passed to other HTML and/or server side script is called parameter passing . -> A session refers to all the connections that a single client might make to a server in the course of viewing any pages associated with a given application.[1] -> Maintenance of user's state during session(e.g.login to logout) is called a Session Tracking .

Ways Visible form parameters Hidden form parameters Cookies Session URL Rewriting

Parameter Passing with <Form> Methods of passing parameters with <form> GET (smaller data i.e.1024 bytes) POST(bigger data, as well as file upload) PHP uses predefined variables $_GET['varname'] $_POST['varname']

Predefined Variables[2] PHP provides a large number of predefined variables represent everything from external variables to built-in environment variables, last error messages to last retrieved headers to all scripts. Superglobals — Superglobals are built-in variables that are always available in all scopes $GLOBALS — References all variables available in global scope $_SERVER — Server and execution environment information $_SERVER — Server and execution environment information $_GET — HTTP GET variables $_POST — HTTP POST variables $_FILES — HTTP File Upload variables

List of predefined variables [2]... $_REQUEST — HTTP Request variables $_SESSION — Session variables $_ENV — Environment variables $_COOKIE — HTTP Cookies $php_errormsg — The previous error message $HTTP_RAW_POST_DATA — Raw POST data $http_response_header — HTTP response headers $argc — The number of arguments passed to script $argv — Array of arguments passed to script

The values of Predefined Variables Values of predefined variables can be seen with <?php phpinfo() ?>

File Upload Writing client's file on the server is called File Upload. In HTML code following is must be added: <form method="post" enctype="multipart/form-data" action="upload.php"> FileName <input type="file" name="userfile"> Above code will display Browse/Choose button on the browser page with which one can select a file.

File Upload HTML page in Browser

Required Configuration in /etc/php.ini File ;file_uploads must be On file_uploads = On ; Temporary directory for HTTP uploaded files (will use system default if not specified). upload_tmp_dir =/tmp ; Maximum allowed size for uploaded files. upload_max_filesize = 2M

Retrieval of File at Server #/uploads must be having o+rwx permission $uploaddir = "/uploads/"; $uploadfile = $uploaddir . basename($_POST["filename"]); if (move_uploaded_file($_FILES["filename"]["tmp_name"], $uploadfile)) { echo "File is valid, and was successfully uploaded.\n"; } else { echo "Possible file upload attack!\n"; }

Session Tracking is done with As HTTP is stateless protocol Session Tracking must be maintained by programmers with following ways: Hidden form parameters Cookies Session URL Rewriting

Hidden Parameter Passing Parameter is passed from 1 page to other which is not visible from user. <input type=hidden name=”username” value=”amichoksi”> Can be retrieved in PHP by $_GET[“username”] $_POST[“username”]

Cookies [2] Cookies are a mechanism for storing data in the remote browser and thus tracking or identifying return users. Set Cookie bool setcookie ( string $name string $value , int $expire=0 , string $path , string $domain , bool $secure=false , bool $httponly=false) setcookie(“username”,”ami”,time()+300); Read Cookie $_COOKIE['name']

Session [2] A way to preserve certain data across subsequent accesses.

Session Functions [2] session_cache_expire — Return current cache expire session_cache_limiter — Get and/or set the current cache limiter session_commit — Alias of session_write_close session_decode — Decodes session data from a string session_destroy — Destroys all data registered to a session session_encode — Encodes the current session data as a string session_get_cookie_params — Get the session cookie parameters session_id — Get and/or set the current session id session_is_registered — Find out whether a global variable is registered in a session session_module_name — Get and/or set the current session module session_name — Get and/or set the current session name session_regenerate_id — Update the current session id with a newly generated one session_register — Register one or more global variables with the current session session_save_path — Get and/or set the current session save path session_set_cookie_params — Set the session cookie parameters session_set_save_handler — Sets user-level session storage functions session_start — Initialize session data session_unregister — Unregister a global variable from the current session session_unset — Free all session variables session_write_close — Write session data and end session

Examples File: Page1.php <?php session_start(); echo 'Welcome to page #1'; $_SESSION['favcolor'] = 'green'; $_SESSION['animal'] = 'cat'; $_SESSION['time'] = time(); session_set_cookie_params(10,"/","sun.com",true, false); ?>

Example... Filename Page2.php session_start(); echo 'Welcome to page #2<br />'; echo $_SESSION['favcolor']; // green echo $_SESSION['animal']; // cat echo date('Y m d H:i:s', $_SESSION['time']);?> session_unset ();//releasing session data Echo $_SESSION['time'];//no output

URL Re-Writing The Apache server’s mod_rewrite module gives the ability to transparently redirect one URL to another by modifying URL (i.e. re-writing), without the user’s knowledge. Used in situations:- Pass some information to other page redirecting old URLs to new addresses Or - cleaning up the ‘dirty’ URLs coming from a poor publishing system

Required Configuration and Examples Following line must be uncommented available in /etc/httpd/conf/httpd.conf file LoadModule rewrite_module modules/mod_rewrite.so URL Rewriting examples http://localhost/ami/123 http://localhost/~ami/UrlRewrite.php?name=amichoksi

Retrieval of URL Rewriting Data <?php if(isset($_SERVER['PATH_INFO'])){ echo $_SERVER['PATH_INFO'];} else if(isset($_GET['username'])) { echo $_GET['username']; } ?>

References http://livedocs.adobe.com/coldfusion/6.1/htmldocs/shared28.htm http://in.php.net/manual/en/

Parameter Passing & Session Tracking in PHP

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