176 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s 176 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s O ffering chat, messaging, and user interaction features are fundamental ways to create addictive content and build up traffic to a site. The phenomenal growth of sites such as MySpace, Facebook, and Twitter (as well as the huge increase in use of instant messaging software) all serve to show that what Internet users love to do more than anything else is communicate with other users. Whether leaving messages, commenting on blogs or web sites, e-mailing, or Tweeting, if you provide the right services, your users will not only take to them, they’ll invite their friends along, too. And presto, you’ll now have free compelling content, as long as you treat your users well and make your web site easy to use. And that’s the aim of this batch of plug-ins: to provide a collection of ready-made functions you can draw on to add the user interaction features your web site needs. Users Online One of the things that drives webmasters crazy is the fact that getting the ball rolling and building up a user base is very hard, but the more users you have the easier it is to get more. Why? One answer has to be that people don’t want to feel alone on a web site. So what better way to reassure them than to display the number of users currently using your web site? And that’s what this plug-in will do for you: It lists the total number of people who have used your web site within a recent period decided by you. Of course, at times when you don’t have many active users you may want to disable this plug-in, or maybe increase the time span during which a visitor is considered recent. But if you do have a few visitors online, discretely displaying the number in a sensible place will reassure them that your web site has something going on. Figure 8-1 shows a web page with five active users. About the Plug-in This plug-in reports the number of users who have recently been active. It takes these arguments: • $datafile A string containing the location of a file for storing the data • $seconds The period of time, in seconds, during which a recent user is considered active FIGURE 8-1 This plug-in provides a quick snapshot of your site’s usage and popularity. 51 C h a p t e r 8 : C h a t a n d M e s s a g i n g 177 C h a p t e r 8 : C h a t a n d M e s s a g i n g 177 Variables, Arrays, and Functions $ip String containing the IP address and the User Agent of the current user $out String containing the contents of the datafile to be written back to the server $online Integer counter containing the number of users online $users Array containing unique user details $usertime String containing time the user being processed last accessed the web site $userip String containing the IP and User Agent string of the user being processed How It Works This plug-in starts by determining the current user’s IP address and User Agent string, as provided by their browser, and then assigning the result to the string $ip. Then a couple of variables are initialized: $out, the contents of the datafile that will be written back, is set to the empty string; and $online, the number of users online is set to 1 (since the program knows that at least the current user is active). If the file $datafile already exists, then there may be previous users who have been active within the last number of seconds specified by $seconds. In which case the contents of $datafile are loaded in, with the last character (a \n linefeed) being removed by the rtrim() function since it is not needed. The result is then split at each remaining \n linefeed into the array $users, so that $users will now have one entry for each user. A foreach loop is then used to iterate through $users, with the details of each one being processed stored in $user. Then the list() function is used to assign $usertime and $userip the time and IP/User Agent details for the user being processed. These are split out of $user using the explode() function with an argument of | (the | symbol being the separator I chose for this plug-in’s data). Then, the current time is looked up using the time() function. If that value, less the value stored in $usertime, is less than the number of seconds stored in $seconds, then that user is considered to still be active, and so their details are appended to the string $out, and the count of active users in $online is incremented. However, if more seconds than the value in $seconds have elapsed since their last access, then they are assumed to no longer be active and their details are forgotten by not appending them to $out. Note how a test is made to ensure the current user’s details are always ignored using the code && $userip != $ip, so that the IP/User Agent details of the user being processed are not the same as the current user’s. This is to ensure those details are removed so they will not be duplicated when the datafile is written back to disk. After completing, the loop $out has the current time and IP/User Agent details appended to it from the function time() and the variable $ip, separated by a | character and terminated with a \n newline. The contents of $out are then saved to the file $datafile, and the number of active users in $online is returned. How to Use It When you want to keep a count of the active users on your web site you should include a call to this plug-in on all your pages where the count is wanted. Doing so is as simple as ensuring the plug-in has been included or pasted, and then using the following code: PIPHP_UsersOnline('users.txt', 300); 178 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s 178 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s Here the 300 represents 300 seconds or five minutes, which is probably a reasonable time window to start with. Whenever you want to know the number of active users, you assign the result returned by the function to a variable, or simply echo it, like this: echo "Users online: " . PIPHP_UsersOnline('users.txt', 300); You can replace the datafile name users.txt with whatever name you prefer. The Plug-in function PIPHP_UsersOnline($datafile, $seconds) { $ip = getenv("REMOTE_ADDR") . getenv("HTTP_USER_AGENT"); $out = ""; $online = 1; if (file_exists($datafile)) { $users = explode("\n", rtrim(file_get_contents($datafile))); foreach($users as $user) { list($usertime, $userip) = explode('|', $user); if ((time() - $usertime) < $seconds && $userip != $ip) { $out .= $usertime . '|' . $userip . "\n"; ++$online; } } } $out .= time() . '|' . $ip . "\n"; file_put_contents($datafile, $out); return $online; } Post to Guestbook No self-respecting web site is complete without some means of providing feedback, so here’s a simple plug-in to enable you to offer a Guestbook feature in just a few lines of PHP code. Figure 8-2 shows the same information posted twice, but because flooding control is enabled, the second post is not added to the Guestbook. About the Plug-in This plug-in posts a message to a Guestbook. It takes these arguments: • $datafile A string containing the location of a file for storing the data • $name The name of the poster 52 C h a p t e r 8 : C h a t a n d M e s s a g i n g 179 C h a p t e r 8 : C h a t a n d M e s s a g i n g 179 • $email The poster’s email address • $website The poster’s website • $message The message to be posted Variables, Arrays, and Functions $data String containing a concatenation of $name, $email, $website, and $message, separated by the token !1! $lines Array containing the messages extracted from $datafile $fh File handle into the file $datafile How It Works This plug-in takes all the data supplied to it, and if it’s not a duplicate of an existing entry, adds it to the datafile. It begins by first creating the line of data to add to $datafile by concatenating the values of $name, $email, $website, and $message, separating them all by the token !1!, which I chose as being unlikely to be ever used in a message or name, and so on. It then places the result in the string $data. Then, if the file $datafile already exists, it is opened and its contents are extracted into the array $lines after the final character, a \n newline character, is removed. The extraction is performed using the explode() function with an argument of \n, newline, the points at which to perform the splitting. Using the function in_array(), each element of $lines is then checked to see whether it already contains the contents of $data. If so, then this would be a duplicate entry and so a value of 0 is returned to indicate the fact, and the post is therefore not added. Otherwise the entry is not a duplicate, so the file handle $fh is assigned the value returned upon opening $datafile for appending, with the fopen() function and an argument of 'a'. If $fh is set to FALSE, then the file could not be opened and so -1 is returned to indicate that fact. FIGURE 8-2 This plug-in provides easy posting to a Guestbook with flood control. 180 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s 180 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s Then the flock() function is called with a parameter of LOCK_EX (for EXclusive lock). This forces the function to wait until all other processes have finished accessing the file. This is done because other users could be posting to the file at the same time and could end up corrupting it. So, once flock() gains control over the file, all other functions that access $datafile using the flock() method will now have to wait their turn. Once the flock() function allows execution to proceed, the fwrite() function is called to write the data in $data to $datafile, followed by a \n newline. This is to separate each line from the next. Because the parameter of 'a' was used with fopen(), this data is appended to the end of the file’s existing contents. Finally, the lock is released using flock() with a parameter of LOCK_UN (for UNlock) and the file is closed. At this point, the write has been made successfully and so a value of 1 is returned. CAUTION The flock() function will not work on NFS and many other networked file systems, or on FAT and its derivatives. Also, when using a multithreaded server API like ISAPI, you may not be able to rely on flock() to protect files against other PHP scripts running in parallel threads of the same server instance. How to Use It To add a post to your Guestbook, you just have to decide on the name of a file in which to store the data and then pass that and the post details to the function PIPHP_PostToGuestBook(), like this: $name = 'F. Gump'; $email = 'run@forestrun.com'; $website = 'http://www.mymommaalwayssaid.com'; $message = 'Life is like a box of chocolates'; $result = PIPHP_PostToGuestBook('guestbook.txt', $name, $email, $website, $message); Of course, when handling user submitted data you will probably also want to sanitize the input using other plug-ins from this book, such as Caps Control or Spell Check from Chapter 3, or some of the Form and User Input plug-ins from Chapter 6, before saving data to the Guestbook. The Plug-in function PIPHP_PostToGuestBook($datafile, $name, $email, $website, $message) { $data = $name . '!1!' . $email . '!1!' . $website . '!1!' . $message; if (file_exists($datafile)) { $lines = explode("\n", rtrim(file_get_contents($datafile))); if (in_array($data, $lines)) return 0; } . online $users Array containing unique user details $usertime String containing time the user being processed last accessed the web site $userip String containing the IP and User Agent string. Functions $ip String containing the IP address and the User Agent of the current user $out String containing the contents of the datafile to be written back to the server $online Integer counter containing. pages where the count is wanted. Doing so is as simple as ensuring the plug- in has been included or pasted, and then using the following code: PIPHP_UsersOnline('users.txt', 300);