PHP1-1 PHP Lecture 2 Xingquan (Hill) Zhu

PHP1-2 PHP  PHP overview  PHP General Syntactic Characteristics  PHP Output to browser  Primitives, Operations, and Expressions  Control Statement  Array  Function  File access  Cookie  Session  Form process

PHP1-3 PHP: Files  Deal with any file on the server $fptr = fopen(filename, use_indicator)  Use indicators:  “r”read only, from the beginning  “r+”read and write, from the beginning  “w”write only, from the beginning (also creates the file, if necessary)  “w+”read and write, from the beginning (also creates the file, if necessary)  “a”write only, at the end, if it exists (creates the file, if necessary)  “a+”read and write, read at the beginning, write at the end  “b”binary file: on systems which differentiate between binary and text files $fptr1=fopen(“test1.php”, “w+”);files.phpfiles.php $fptr2=fopen(“test1.php”, “r+”);

PHP1-4 PHP: Files  fopen could fail  it will return “false”  Use file_exists(filename) to determine whether file exists before trying to open it  Use fopen with “die”  Always use fclose(file_var) to close a file, after your reading/writing Fopen.php

PHP1-5 PHP: Write to Files  $bytes_written = fwrite(file_var, string)  fwrite returns the number of bytes it wrote  Return “false” on error fwrite.php

PHP1-6 PHP: Reading Files  Read all or part of the file into a string variable  $str = fread(file_var, #bytes)  To read the whole file, use filesize(file_name) as the second parameter  Read one line from the file  $line = fgets(file_var[, #bytes])  Reads characters until eoln, eof, or #bytes characters have been read  Read one character from the file  $ch = fgetc(file_var) Control reading lines or characters with eof detection using feof (TRUE for eof; FALSE otherwise) while(!feof($file_var)) { $ch = fgetc($file_var); } Readingfile.php

PHP1-7 PHP file access  Read the lines of the file into an array  array file ( string filename) file() returns the file in an array Each element of the array corresponds to a line in the file, with the newline still attached. Upon failure, file() returns FALSE File.phpFiltering.php

PHP1-8 PHP  PHP overview  PHP General Syntactic Characteristics  PHP Output to browser  Primitives, Operations, and Expressions  Control Statement  Array  Function  File access  Cookie  Session  Form process

PHP1-9 Building a Shopping Cart  What is a shopping cart  Putting things together and then check out.  A series of scripts that keep track of items a visitor picks to buy from your site until they proceed to the "checkout  Web server is basically stateless  HTTP is stateless  It does not store any information about a web client Why?  Web server records nothing about the previous actions of a web client It only knows the current web page the web browser is visiting  How are we going to keep our browser “continuously” connected to the server  So we can feel the we are connected to the server all the time  How are we going to collect information across different web pages  Cookie & Session  Hidden fields of a form

PHP1-10 Cookie  What is a cookie?  An message given to a web browser by a web server, then send back to the server each time the browser requests a page from the server.  What can cookie do for us?  Identify users and store client side information  Authenticate or identify a registered user No need to sign in again every time they access a website  Where is the cookie located? How does it look like?  C:\Documents and Settings\YourLoginID\Local Settings\Temporary Internet Files   Will browser return all cookies to each server?  No, only those matched domains  Malicious cookies setting  Are cookies dangerous to my computer?  No  Is this a major privacy issue?  You could lose identify information  You have choices of not using any cookie

PHP1-11 Cookie  Create a cookie with setcookie  setcookie(cookie_name, cookie_value, lifetime) setcookie("voted", "true", time() ); setcookie("voted", "true", time() + 60*60*24);  Is “lifetime” important? Without this value, cookie expires right after you close the current web browser window. Expired cookies will be deleted without sending back to the server  Cookies must be created before any other HTML is created by the script  Before …were sent  How to access the cookie value  Using the $_COOKIE array setcookie("visits“, $visitcount, time()+3600); $visitcount = $_COOKIE["visits"];  Check whether a cookie has been set before Isset($_COOKIE[“visits”]) Cookie_simple.phpcookie1.php

PHP1-12 Simple Shopping Cart  How to update cookie value based on your choice?  $_SERVER["PHP_SELF"] The name of the current script  Using implicit arrays for form values $_POST $_GET Simpleupdate.php Updatecookie.phpuppdatecookie1.php

PHP1-13 Simple Shopping Cart  At checkout page, summarize all the cookie values Checkout.phpcheckout1.php Checkoutmain.php

PHP1-14 Session Tracking  What is a session  SUN API: Provides a way to identify a user across more than one page request or visit to a Web site and to store information about that user  web applications make use of sessions to remember who you are  A session is available as long as the browser is opened  A session is closed as soon as the browser is closed or you go to another website  Why session?  Some users block cookies for privacy concerns  Are cookie & session same thing?  Cookie cookies are normally stored in your hard disk privacy  Session A session aren't stored in your hard disk Considered more secure

PHP1-15 Session tracking  For session tracking, PHP creates and maintains a session tracking id  Create the id with a call to session_start with no parameters  Subsequent calls to session_start retrieves any session variables that were previously registered in the session  To create a session variable  $_SESSION['myVar'] = $myVarValue;  Check session if(isset($_SESSION['myVar'])) { print $_SESSION['myVar']; $_SESSION['myVar']++; }  Example: count number of pages visited Session.phpmain_1.phpmain_2.php

PHP1-16 Form Process  Action property  Where to send form data  Method property  Post vs get  Each element has unique name  Using implicit arrays for form element access $_POST $_GET Simpleform.htmlsimpleform.php

PHP1-17 A complete Shopping Cart  Client Side:  Set cookie for each page  Collect information across web pages  A summarization form (before user submit the order)  “Submission” -> invoke form processing program  Server Side:  A form processing program  Read form values from $_POST or $_GET array  Process and save values  Confirmation formselection.phpformselection.php formselection1.php formprocess.phpformselection1.php formprocess.php

PHP1-18 PHP  PHP overview  PHP General Syntactic Characteristics  PHP Output to browser  Primitives, Operations, and Expressions  Control Statement  Array  Function  File access  Cookie  Session  Form process