Phát triển web với PHP và MySQL - p 77 ppt

First, look at the URL: http://webserver/chapter29/new_post.php?parent=5 The parameter passed in as parent will be the parent postid of the new posting. If you click New Post instead of Reply, you will get parent=0 in the URL. Second, you will see that for a reply, the text of the original message is inserted and marked with a “>” character as is the case in most mail and news reading programs. Third, you can see that the title of this message defaults to the title of the original message pre- fixed with “Re:”. Let’s look at the code that produces this output. It is shown in Listing 29.8. LISTING 29.8 new_post.php—Allows a User to Type a New Post or Reply to an Existing Post <? include (‘include_fns.php’); if(!$area) $area = 1; if(!$error) { if(!$parent) { $parent = 0; if(!$title) $title = “New Post”; } else { // get post name $title = get_post_title($parent); // append Re: if(strstr($title, “Re: “) == false ) $title = “Re: “.$title; //make sure title will still fit in db $title = substr($title, 0, 20); //prepend a quoting pattern to the post you are replying to $message = add_quoting(get_post_message($parent)); } } Building Web Forums C HAPTER 29 29 BUILDING WEB FORUMS 735 35 7842 CH29 3/6/01 3:34 PM Page 735 do_html_header(“$title”); display_new_post_form($parent, $area, $title, $message, $name); if($error) echo “Your message was not stored. Make sure you have filled in all fields and try again.”; do_html_footer(); ?> After some initial setting up, this script checks whether the parent is zero or otherwise. If it is zero, this is a new topic, and little further work is needed. If this is a reply ($parent is the postid of an existing article), then the script goes ahead and sets up the title and the text of the original message, as follows: // get post name $title = get_post_title($parent); // append Re: if(strstr($title, “Re: “) == false ) $title = “Re: “.$title; //make sure title will still fit in db $title = substr($title, 0, 20); //prepend a quoting pattern to the post you are replying to $message = add_quoting(get_post_message($parent)); The functions it uses here are get_post_title(), get_post_message(), and add_quoting(). These functions are all from the discussion_fns.php library. They are shown in Listings 29.9, 29.10, and 29.11, respectively. LISTING 29.9 get_post_title() Function from discussion_fns.php—Retrieves a Message’s Title from the Database function get_post_title($postid) { // extract one post’s name from the database if(!$postid) return “”; $conn = db_connect(); Building Practical PHP and MySQL Projects P ART V 736 LISTING 29.8 Continued 35 7842 CH29 3/6/01 3:34 PM Page 736 //get all header information from ‘header’ $query = “select title from header where postid = $postid”; $result = mysql_query($query); if(mysql_numrows($result)!=1) return “”; return mysql_result($result, 0, 0); } LISTING 29.10 get_post_message() Function from discussion_fns.php—Retrieves a Message’s Body from the Database function get_post_message($postid) { // extract one post’s message from the database if(!$postid) return “”; $conn = db_connect(); $query = “select message from body where postid = $postid”; $result = mysql_query($query); if(mysql_numrows($result)>0) { return mysql_result($result,0,0); } } These first two functions retrieve an article’s header and body (respectively) from the database. LISTING 29.11 add_quoting() Function from discussion_fns.php—Indents a Message Text with “>” Symbols function add_quoting($string, $pattern = “> “) { // add a quoting pattern to mark text quoted in your reply return $pattern.str_replace(“\n”, “\n$pattern”, $string); } The add_quoting() function reformats the string to begin each line of the original text with a symbol, which defaults to >. Building Web Forums C HAPTER 29 29 BUILDING WEB FORUMS 737 LISTING 29.9 Continued 35 7842 CH29 3/6/01 3:34 PM Page 737 After the user types in his reply and clicks the Post button, he will be taken to the store_new_post.php script. Sample output from this script is shown in Figure 29.9. Building Practical PHP and MySQL Projects P ART V 738 FIGURE 29.9 The new post is now visible in the tree. The new post is there in the figure, under Re: using gd? - Laura - 08:28 09/26/2000. Other than that, this page looks like the regular index.php page. Let’s look at the code for store_new_post.php. It is shown in Listing 29.12. LISTING 29.12 store_new_post.php—Puts the New Post in the Database <? include (“include_fns.php”); if($id = store_new_post($HTTP_POST_VARS)) { include (“index.php”); } else { $error = true; include (“new_post.php”); } ?> 35 7842 CH29 3/6/01 3:34 PM Page 738 As you can see, this is a short script. Its main task is to call the store_new_post() function. This page has no visual content of its own. If storing succeeds, we see the index page. Otherwise, we go back to the new_post.php page, so the user can try again. The store_new_post() function is shown in Listing 29.13. LISTING 29.13 store_new_post() Function from discussion_fns.php—Validates and Stores the New Post in the Database function store_new_post($post) { // validate clean and store a new post $conn = db_connect(); // check no fields are blank if(!filled_out($post)) return false; $post = clean_all($post); //check parent exists if($post[“parent”]!=0) { $query = “select postid from header where postid = ‘“.$post[‘parent’].”’”; $result = mysql_query($query); if(mysql_numrows($result)!=1) { return false; } } // check not a duplicate $query = “select header.postid from header, body where header.postid = body.postid and header.parent = “.$post[‘parent’].” and header.poster = ‘“.$post[‘poster’].”’ and header.title = ‘“.$post[‘title’].”’ and header.area = “.$post[‘area’].” and body.message = ‘“.$post[‘message’].”’”; $result = mysql_query($query); if (!$result) { return false; } if(mysql_numrows($result)>0) return mysql_result($result, 0, 0); Building Web Forums C HAPTER 29 29 BUILDING WEB FORUMS 739 35 7842 CH29 3/6/01 3:34 PM Page 739 $query = “insert into header values (‘“.$post[‘parent’].”’, ‘“.$post[‘poster’].”’, ‘“.$post[‘title’].”’, 0, ‘“.$post[‘area’].”’, now(), NULL )”; $result = mysql_query($query); if (!$result) { return false; } // note that our parent now has a child $query = “update header set children = 1 where postid = “.$post[‘parent’]; $result = mysql_query($query); if (!$result) { return false; } // find our post id, note that there could be multiple headers // that are the same except for id and probably posted time $query = “select header.postid from header left join body on header.postid = body.postid where parent = ‘“.$post[“parent”].”’ and poster = ‘“.$post[“poster”].”’ and title = ‘“.$post[“title”].”’ and body.postid is NULL”; $result = mysql_query($query); if (!$result) { return false; } if(mysql_numrows($result)>0) $id = mysql_result($result, 0, 0); if($id) { $query = “insert into body values ($id, ‘“.$post[“message”].”’)”; $result = mysql_query($query); if (!$result) { Building Practical PHP and MySQL Projects P ART V 740 LISTING 29.13 Continued 35 7842 CH29 3/6/01 3:34 PM Page 740 return false; } return $id; } } This is a long function, but it is not overly complex. It is only long because inserting a posting means inserting entries in the header and body tables, and updating the parent article’s row in the header table to show that it now has children. That is the end of the code for the Web forum application. Extensions There are many extensions you could add to this project: • You could add navigation to the view options, so that from a post you could navigate to the next message, the previous message, the next-in-thread message, or the previous-in- thread message. • You could add an administration interface for setting up new forums and deleting old posts. • You could add user authentication so only registered users could post. • You could add some kind of moderation or censorship mechanism. Look at existing systems for ideas. Using an Existing System There are a couple of noteworthy existing systems. Phorum is an Open Source Web forums project. It has different navigation and semantics from ours, but its structure is relatively easily customized to fit into your own site. A notable feature of phorum is that it can be configured by the actual user to display in either a threaded or flat view. You can find out more about it at http://www.phorum.org Another interesting project is phpslash. This is a port of the software used to run the Slashdot discussion boards. Although the original software is written in Perl, this PHP version is avail- able. You can get it from http://www.phpslash.org Building Web Forums C HAPTER 29 29 BUILDING WEB FORUMS 741 LISTING 29.13 Continued 35 7842 CH29 3/6/01 3:34 PM Page 741 Next In Chapter 30, “Generating Personalized Documents in Portable Document Format (PDF),” we will use the PDF format to deliver documents that are attractive, print consistently and are somewhat tamperproof. This is useful for a range of service-based applications, such as gener- ating contracts online. Building Practical PHP and MySQL Projects P ART V 742 35 7842 CH29 3/6/01 3:34 PM Page 742 CHAPTER 30 Generating Personalized Documents in Portable Document Format (PDF) 36 7842 CH30 3/6/01 3:40 PM Page 743 On service driven sites, we sometimes need to deliver personalized documents, generated in response to input from our visitors. This can be used to provide an automatically filled in form or to generate personalized documents, such as legal documents, letters, or certificates. Our example in this chapter will present a user with an online skill assessment page and generate a certificate. We will explain • How to use PHP string processing to integrate a template with a user’s data to create a Rich Text Format (RTF) document • How to use a similar approach to generate a Portable Document Format (PDF) document • How to use PHP’s PDFlib functions to generate a similar PDF document The Problem We want to be able to give our visitors an exam consisting of a number of questions. If they answer enough of the questions correctly, we will generate a certificate for them to show that they have passed the exam. So that a computer can mark them easily, our questions will be multiple choice, consisting of a question and a number of potential answers. Only one of the potential answers for each question will be correct. If a user achieves a passing grade on the questions, he will be presented with a certificate. Ideally, the file format for our certificate should 1. Be easy to design 2. Be able to contain a variety of different elements such as bitmap and vector images 3. Result in a high quality printout 4. Only require a small file to be downloaded 5. Be generated almost instantly 6. Be at a low cost to produce 7. Work on many operating systems 8. Be difficult to fraudulently duplicate or modify 9. Not require any special software to view or print 10. Display and print consistently for all recipients Like many decisions we need to make from time to time, we will probably need to compro- mise when choosing a delivery format to meet as many of these ten attributes as possible. Building Practical PHP and MySQL Projects P ART V 744 36 7842 CH30 3/6/01 3:40 PM Page 744 . store_new_post .php Puts the New Post in the Database <? include (“include_fns .php ); if($id = store_new_post($HTTP_POST_VARS)) { include (“index .php ); } else { $error = true; include (“new_post .php ); } ?> 35. the store_new_post .php script. Sample output from this script is shown in Figure 29.9. Building Practical PHP and MySQL Projects P ART V 738 FIGURE 29.9 The new post is now visible in the tree. The new post. URL: http://webserver/chapter29/new_post .php? parent=5 The parameter passed in as parent will be the parent postid of the new posting. If you click New Post instead of Reply, you will get parent=0