//the first three lines are name, instructor’s email, and password $quizName = fgets($msfp); $quizEmail = fgets($msfp); $quizPwd = fgets($msfp); The master file is opened with read access. The first three lines are unimportant, but I must read them to get to the quiz data. Creating an Answer Key I start by generating an answer key from the master file, stepping through each question in the file and extracting all the normal variables from it (although I’m interested only in the $correct variable). I then store the $correct value in an array called $key. At the end of this loop, the $key array holds the correct answer for each quiz question. //step through the questions building an answer key $numCorrect = 0; $questionNumber = 1; while (!feof($msfp)){ $currentProblem = fgets($msfp); list($question, $answerA, $answerB, $answerC, $answerD, $correct) = split (“:”, $currentProblem); $key[$questionNumber] = $correct; $questionNumber++; } // end while fclose($msfp); Checking the User’s Response The user’s responses come from the HTML form as an array called $quest. The cor- rect answers are in an array called $key. To grade the test, I step through both arrays at the same time, comparing the user’s response with the correct response. Each time these values are the same, the user has gotten an answer cor- rect. The user was incorrect when the values are different or there was a problem with the test itself; don’t discount that as a possibility. Unfortunately, you can’t do much about that, because the test author is responsible for making sure the test is correct. Still, you might be able to improve the situation somewhat by pro- viding a better editor that ensures the test is in the right format and each ques- tion has an answer registered with it. 223 C h a p t e r 6 W o r k i n g w i t h F i l e s //Check each answer from user for ($questionNumber = 1; $questionNumber <= count($quest); $questionNumber++){ $guess = $quest[$questionNumber]; $correct = $key[$questionNumber]; $correct = rtrim($correct); if ($guess == $correct){ //user got it right $numCorrect++; print “problem # $questionNumber was correct<br>\n”; } else { print “<font color = red>problem # $questionNumber was incorrect</font><br>\n”; } // end if } // end for I give a certain amount of feedback, telling whether the question was correct, but I decide not to display the right answer. You might give the user more or less information, depending on how you’re using the quiz program. Reporting the Results to Screen and Log File After checking each answer, the program reports the results to the user as a raw score and a percentage. The program also opens a log file for append access and adds the current data to it. Append access is just like write access, but rather than overwriting an existing file, it adds any new data to the end of it. print “you got $numCorrect right<br>\n”; $percentage = ($numCorrect /count($quest)) * 100; print “for $percentage percent<br>\n”; $today = date (“F j, Y, g:i a”); //print “Date: $today<br>\n”; $location = getenv(“REMOTE_ADDR”); //print “Location: $location<br>\n”; //add results to log file $lgfp = fopen($logFile, “a”); $logLine = $student . “\t”; $logLine .= $today . “\t”; $logLine .= $location . “\t”; $logLine .= $numCorrect . “\t”; 224 P H P 5 /M y S Q L P r o g r a m m i n g f o r t h e A b s o l u t e B e g i n n e r $logLine .= $percentage . “\n”; fputs($lgfp, $logLine); fclose($lgfp); ?> </html> I add a few more elements to the log file that might be useful to a test adminis- trator. Of course, I add the student’s name and current date. I also added a loca- tion variable, which uses the $ REMOTE_ADDR environment variable to indicate which machine the user was on when she submitted the exam. This can be use- ful because it can alert you to certain kinds of hacking. (A person taking the same quiz several times on the same machine but with a different name, for example.) The gradeQuiz program adds the number correct and the percentage to the log file as well, then closes the file. Notice that the data in the log file is delimited with tab characters. This is done so an analysis program could easily work with the file using the split command. Also, most spreadsheet programs can read a tab-delimited file, so the log file is easily imported into a spreadsheet for further analysis. Look at the PHP online Help for the date functions to see all the ways you can dis- play the current date. You can really improve the logging functionality if you want to do some in-depth test analysis. For example, store each user’s response to each question in the quiz. This gives you a database of performance on every question, so you could easily determine which questions are causing difficulty. Viewing the Log The showLog.php program is actually very similar to the takeQuiz program. It checks the password to ensure the user has administrator access, then opens the log using the file() function. It prints the file results inside a <pre></pre> pair, so the tab characters are preserved. <? //showLog.php //shows a log file TRICK TRICK 225 C h a p t e r 6 W o r k i n g w i t h F i l e s //requires admin password if ($password == “absolute”){ $lines = file($logFile); print “<pre>\n”; foreach ($lines as $theLine){ print $theLine; } // end foreach print “</pre>\n”; } else { print <<<HERE <font color = “red” size = +2> You must have the appropriate password to view this log </font> HERE; } // end if ?> Improve this program by writing the data into an HTML table. However, not all spreadsheets can easily work with HTML table data, so I prefer the tab format. It isn’t difficult to add data analysis to the log viewer, including mean scores, stan- dard deviation, and suggested curve values. Summary This chapter explores the use of sequential files as a data storage and retrieval mechanism. You learned how to open files in read, write, and append modes and you know how file pointers refer to a file. You wrote data to a file and loaded data from a file with appropriate functions. You learned how to load an entire file into an array. You can examine a directory and determine which files are in the directory. You learned how to use basic regular expressions in the preg_greq() function to display a subset of files in the directory. Finally, you put all this together in a multi-program system that allows multiple levels of access to an interesting data set. You should be proud. 226 P H P 5 /M y S Q L P r o g r a m m i n g f o r t h e A b s o l u t e B e g i n n e r 227 C h a p t e r 6 W o r k i n g w i t h F i l e s CHALLENGES 1. Improve the quiz program in one of the ways I suggested throughout the chapter: Add the ability to e-mail test results, put in some test scores analysis, improve the quiz editing page, or try something of your own. 2. A couple of values in this system should be global among each of the PHP programs. The root directory of the files and the administrative password are obvious candidates. Write a program that stores these values in an .ini file and modify the quiz programs to get these values from that file when needed. 3. Create a source code viewer. Given a filename, the program should read in the file and convert each instance of < into <. Save this new file to another name. This allows you to show your source code to others. 4. Create a simple guest book. Let the user enter information into a form, and add her comment to the bottom of the page when she clicks the submit button. You can use one or two files for this. . tab-delimited file, so the log file is easily imported into a spreadsheet for further analysis. Look at the PHP online Help for the date functions to see all the ways you can dis- play the current date. You. you could easily determine which questions are causing difficulty. Viewing the Log The showLog .php program is actually very similar to the takeQuiz program. It checks the password to ensure the. results inside a <pre></pre> pair, so the tab characters are preserved. <? //showLog .php //shows a log file TRICK TRICK 225 C h a p t e r 6 W o r k i n g w i t h F i l e s //requires