In this tutorial, we're going to
build a PHP/MySQL powered forum from scratch. This tutorial is perfect
for getting used to basic PHP and database usage. Let's dive right in!
Looks pretty neat, huh? Every square is a database table. All the columns are listed in it and the lines between them represent the relationships. I'll explain them further, so it's okay if it doesn't make a lot of sense to you right now.
I'll discuss each table by explaining the SQL, which I created using the scheme above. For your own scripts you can create a similar scheme and SQL too. Some editors like MySQL Workbench (the one I used) can generate .sql files too, but I would recommend learning SQL because it's more fun to do it yourself. A SQL introduction can be found at W3Schools.
The CREATE TABLE statement is used to indicate we want to create a new
table, of course. The statement is followed by the name of the table and
all the columns are listed between the brackets. The names of all the
fields are self-explanatory, so we'll only discuss the data types below.
There is a user called John Doe. If another users registers with the same name, there's a problem, because: which user is which? You can't tell and the database can't tell either. By using a primary key this problem is solved, because both topics are unique.
All the other tables have got primary keys too and they work the same way.
These data types basically work the same way as the ones in the users
table. This table also has a primary key and the name of the category
must be an unique one.
This table is almost the same as the other tables, except for the
topic_by field. That field refers to the user who created the topic. The
topic_cat refers to the category the topic belongs to. We cannot force
these relationships by just declaring the field. We have to let the
database know this field must contain an existing user_id from the users
table, or a valid cat_id from the categories table. We'll add some
relationships after I've discussed the posts table.
This is the same as the rest of the tables; there's also a field which
refers to a user_id here: the post_by field. The post_topic field refers
to the topic the post belongs to.
We'll link the topics to the categories first:
The last part of the query already says what happens. When a category
gets deleted from the database, all the topics will be deleted too. If
the cat_id of a category changes, every topic will be updated too.
That's what the ON UPDATE CASCADE part is for. Of course, you can
reverse this to protect your data, so that you can't delete a category
as long as it still has topics linked to it. If you would want to do
that, you could replace the 'ON DELETE CASCADE' part with 'ON DELETE
RESTRICT'. There is also SET NULL and NO ACTION, which speak for
themselves.
Every topic is linked to a category now. Let's link the topics to the user who creates one.
This foreign key is the same as the previous one, but there is one
difference: the user can't be deleted as long as there are still topics
with the user id of the user. We don't use CASCADE here because there
might be valuable information in our topics. We wouldn't want that
information to get deleted if someone decides to delete their account.
To still give users the opportunity to delete their account, you could
build some feature that anonymizes all their topics and then delete
their account. Unfortunately, that is beyond the scope of this tutorial.
Link the posts to the topics:
And finally, link each post to the user who made it:
That's the database part! It was quite a lot of work, but the result, a great data model, is definitely worth it.
The wrapper div will be used to make it easier to style the entire
page. The menu div obviously contains a menu with links to pages we
still have to create, but it helps to see where we're going a little
bit. The userbar div is going to be used for a small top bar which
contains some information like the username and a link to the logout
page. The content page holds the actual content of the page, obviously.
The attentive reader might have already noticed we're missing some things. There is no
When we include a header and a footer on each page the rest of the
page get embedded between the header and the footer. This method has got
some advantages. First and foremost, everything will be styled
correctly. A short example:
As you can see, a page without errors will result in a nice page with
the content. But if there's an error, everything looks really ugly; so
that's why it's better to make sure not only real content is styled
correctly, but also the errors we might get.
Another advantage is the possibility of making quick changes. You can see for yourself by editing the text in footer.php when you've finished this tutorial; you'll notice that the footer changes on every page immediately. Finally, we add a stylesheet which provides us with some basic markup - nothing too fancy.
Simply replace the default values of the variables at the top of the
page with your own date, save the file and you're good to go!
There you have it: a nice and clean overview. We'll be updating this
page throughout the tutorial so that it becomes more like the end
result, step by step!
A PHP page is needed to process the form. We're going to use a $_SERVER variable. The $_SERVER variable is an array with values that are automatically set with each request. One of the values of the $_SERVER array is 'REQUEST_METHOD'. When a page is requested with GET, this variable will hold the value 'GET'. When a page is requested via POST, it will hold the value 'POST'. We can use this value to check if a form has been posted. See the signup.php page below.
A lot of explanation is in the comments I made in the file, so be sure
to check them out. The processing of the data takes place in three
parts:
On line 1 we have the INSERT INTO statement which speaks for itself.
The table name is specified on the second line. The words between the
brackets represent the columns in which we want to insert the data. The
VALUES statement tells the database we're done declaring column names
and it's time to specify the values. There is something new here:
mysql_real_escape_string. The function escapes special characters in an
unescaped string , so that it is safe to place it in a query. This
function MUST always be used, with very few exceptions. There are too
many scripts that don't use it and can be hacked real easy. Don't take
the risk, use mysql_real_escape_string().
Note: it's also possible to use md5(), I always use sha1() because benchmarks have proved it's a tiny bit faster, not much though. You can replace sha1 with md5 if you like.
If the signup process was successful, you should see something like this:
Try refreshing your phpMyAdmin screen, a new record should be visible in the users table.
Now that you've completed the previous step, we're going to make your freshly created account an admin account. In phpMyAdmin, click on the users table, and then 'Browse'. Your account will probably pop up right away. Click the edit icon and change the value of the user_level field from 0 to 1. That's it for now. You won't notice any difference in our application immediately, but when we've added the admin features a normal account and your account will have different capabilities.
The sign-in process works the following way:
The signin.php file is below. Don't think I'm not explaining what I'm doing, but check out the comments in the file. It's much easier to understand that way.
This is the query that's in the signin.php file:
It's obvious we need a check to tell if the supplied credentials
belong to an existing user. A lot of scripts retrieve the password from
the database and compare it using PHP. If we do this directly via SQL
the password will be stored in the database once during registration and
never leave it again. This is safer, because all the real action
happens in the database layer and not in our application.
If the user is signed in successfully, we're doing a few things:
First, we set the 'signed_in' $_SESSION var to true, so we can use it
on other pages to make sure the user is signed in. We also put the
username and user id in the $_SESSION variable for usage on a different
page. Finally, we display a link to the forum overview so the user can
get started right away.
Of course signing in requires another function, signing out! The sign-out process is actually a lot easier than the sign-in process. Because all the information about the user is stored in $_SESSION variables, all we have to do is unset them and display a message.
Now that we've set the $_SESSION variables, we can determine if someone is signed in. Let's make a last simple change to header.php:
Replace:
With:
If a user is signed in, he will see his or her name displayed on the
front page with a link to the signout page. Our authentication is done!
By now our forum should look like this:
This step looks a lot like Step 4 (Signing up a user'), so I'm not
going to do an in-depth explanation here. If you followed all the steps
you should be able to understand this somewhat quickly.
As you can see, we've started the script with the $_SERVER check,
after checking if the user has admin rights, which is required for
creating a category. The form gets displayed if it hasn't been submitted
already. If it has, the values are saved. Once again, a SQL query is
prepared and then executed.
This query selects all categories and their names and descriptions
from the categories table. We only need a bit of PHP to display the
results. If we add that part just like we did in the previous steps, the
code will look like this.
Notice how we're using the cat_id to create links to category.php. All the links to this page will look like this: category.php?cat_id=x,
where x can be any numeric value. This may be new to you. We can check
the url with PHP for $_GET values. For example, we have this link:
The statement echo $_GET[ëcat_id'];' will display '23'. In the next
few steps we'll use this value to retrieve the topics when viewing a
single category, but topics can't be viewed if we haven't created them
yet. So let's create some topics!
The structure of create_topic.php can hardly be explained in a list or something, so I rewrote it in pseudo-code.
Here's the real code of this part of our forum, check the explanations below the code to see what it's doing.
I'll discuss this page in two parts, showing the form and processing the form.
Showing the form
We're starting with a simple HTML form. There is actually something special here, because we use a dropdown. This dropdown is filled with data from the database, using this query:
That's the only potentially confusing part here; it's quite a piece of code, as you can see when looking at the create_topic.php file at the bottom of this step.
Processing the form
The process of saving the topic consists of two parts: saving the topic in the topics table and saving the first post in the posts table. This requires something quite advanced that goes a bit beyond the scope of this tutorial. It's called a transaction, which basically means that we start by executing the start command and then rollback when there are database errors and commit when everything went well. More about transactions.
The first query being used to save the data is the topic creation query, which looks like this:
At first the fields are defined, then the values to be inserted. We've
seen the first one before, it's just a string which is made safe by
using mysql_real_escape_string(). The second value, NOW(), is a SQL
function for the current time. The third value, however, is a value we
haven't seen before. It refers to a (valid) id of a category. The last
value refers to an (existing) user_id which is, in this case, the value
of $_SESSION[ëuser_id']. This variable was declared during the sign in
process.
If the query executed without errors we proceed to the second query. Remember we are still doing a transaction here. If we would've got errors we would have used the ROLLBACK command.
The first thing we do in this code is use mysql_insert_id() to
retrieve the latest generated id from the topic_id field in the topics
table. As you may remember from the first steps of this tutorial, the id
is generated in the database using auto_increment.
Then the post is inserted into the posts table. This query looks a lot like the topics query. The only difference is that this post refers to the topic and the topic referred to a category. From the start, we decided to create a good data model and here is the result: a nice hierarchical structure.
A short list of the things we need:
The query above selects all the categories from the database.
The query above is executed in the while loop in which we echo the
categories. By doing it this way, we'll see all the categories and the
latest topic for each of them.
The complete code of category.php will be the following:
And here is the final result of our categories page:
This information is displayed in the head of the table we will use to
display all the data. Next, we retrieve all the posts in this topic from
the database. The following query gives us exactly what we need:
This time, we want information from the users and the posts table - so
we use the LEFT JOIN again. The condition is: the user id should be the
same as the post_by field. This way we can show the username of the
user who replied at each post.
The final topic view looks like this:
The complete reply.php code looks like this.
The comments in the code pretty much detail what's happening. We're
checking for a real user and then inserting the post into the database.
Step 1: Creating Database Tables
It's always a good idea to start with creating a good data model when building an application. Let's describe our application in one sentence: We are going to make a forum which has users who create topics in various categories. Other users can post replies. As you can see, I highlighted a couple of nouns which represent our table names.Users
- Categories
- Topics
- Posts
Looks pretty neat, huh? Every square is a database table. All the columns are listed in it and the lines between them represent the relationships. I'll explain them further, so it's okay if it doesn't make a lot of sense to you right now.
I'll discuss each table by explaining the SQL, which I created using the scheme above. For your own scripts you can create a similar scheme and SQL too. Some editors like MySQL Workbench (the one I used) can generate .sql files too, but I would recommend learning SQL because it's more fun to do it yourself. A SQL introduction can be found at W3Schools.
Users Table
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| CREATE TABLE users ( user_id INT (8) NOT NULL AUTO_INCREMENT, user_name VARCHAR (30) NOT NULL , user_pass VARCHAR (255) NOT NULL , user_email VARCHAR (255) NOT NULL , user_date DATETIME NOT NULL , user_level INT (8) NOT NULL , UNIQUE INDEX user_name_unique (user_name), PRIMARY KEY (user_id) ) TYPE=INNODB; |
user_id
"A primary key is used to uniquely identify each row in a table."The type of this field is INT, which means this field holds an integer. The field cannot be empty (NOT NULL) and increments which each record inserted. At the bottom of the table you can see the user_id field is declared as a primary key. A primary key is used to uniquely identify each row in a table. No two distinct rows in a table can have the same value (or combination of values) in all columns. That might be a bit unclear, so here's a little example.
There is a user called John Doe. If another users registers with the same name, there's a problem, because: which user is which? You can't tell and the database can't tell either. By using a primary key this problem is solved, because both topics are unique.
All the other tables have got primary keys too and they work the same way.
user_name
This is a text field, called a VARCHAR field in MySQL. The number between brackets is the maximum length. A user can choose a username up to 30 characters long. This field cannot be NULL. At the bottom of the table you can see this field is declared UNIQUE, which means the same username cannot be registered twice. The UNIQUE INDEX part tells the database we want to add a unique key. Then we define the name of the unique key, user_name_unique in this case. Between brackets is the field the unique key applies to, which is user_name.user_pass
This field is equal to the user_name field, except the maximum length. Since the user password, no matter what length, is hashed with sha1(), the password will always be 40 characters long.user_email
This field is equal to the user_pass field.user_date
This is a field in which we'll store the date the user registered. It's type is DATETIME and the field cannot be NULL.user_level
This field contains the level of the user, for example: '0' for a regular user and '1' for an admin. More about this later.Categories Table
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| CREATE TABLE categories ( cat_id INT (8) NOT NULL AUTO_INCREMENT, cat_name VARCHAR (255) NOT NULL , cat_description VARCHAR (255) NOT NULL , UNIQUE INDEX cat_name_unique (cat_name), PRIMARY KEY (cat_id) ) TYPE=INNODB; |
Topics Table
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| CREATE TABLE topics ( topic_id INT (8) NOT NULL AUTO_INCREMENT, topic_subject VARCHAR (255) NOT NULL , topic_date DATETIME NOT NULL , topic_cat INT (8) NOT NULL , topic_by INT (8) NOT NULL , PRIMARY KEY (topic_id) ) TYPE=INNODB; |
Posts Table
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| CREATE TABLE posts ( post_id INT (8) NOT NULL AUTO_INCREMENT, post_content TEXT NOT NULL , post_date DATETIME NOT NULL , post_topic INT (8) NOT NULL , post_by INT (8) NOT NULL , PRIMARY KEY (post_id) ) TYPE=INNODB; |
"A foreign key is a referential constraint between two tables. The foreign key identifies a column or a set of columns in one (referencing) table that refers to a column or set of columns in another (referenced) table."Now that we've executed these queries, we have a pretty decent data model, but the relations are still missing. Let's start with the definition of a relationship. We're going to use something called a foreign key. A foreign key is a referential constraint between two tables. The foreign key identifies a column or a set of columns in one (referencing) table that refers to a column or set of columns in another (referenced) table. Some conditions:
- The column in the referencing table the foreign key refers to must be a primary key
- The values that are referred to must exist in the referenced table
We'll link the topics to the categories first:
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| ALTER TABLE topics ADD FOREIGN KEY (topic_cat) REFERENCES categories(cat_id) ON DELETE CASCADE ON UPDATE CASCADE ; |
Every topic is linked to a category now. Let's link the topics to the user who creates one.
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| ALTER TABLE topics ADD FOREIGN KEY (topic_by) REFERENCES users(user_id) ON DELETE RESTRICT ON UPDATE CASCADE ; |
Link the posts to the topics:
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| ALTER TABLE posts ADD FOREIGN KEY (post_topic) REFERENCES topics(topic_id) ON DELETE CASCADE ON UPDATE CASCADE ; |
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| ALTER TABLE posts ADD FOREIGN KEY (post_by) REFERENCES users(user_id) ON DELETE RESTRICT ON UPDATE CASCADE ; |
Step 2: Introduction to the Header/Footer System
Each page of our forum needs a few basic things, like a doctype and some markup. That's why we'll include a header.php file at the top of each page, and a footer.php at the bottom. The header.php contains a doctype, a link to the stylesheet and some important information about the forum, such as the title tag and metatags.header.php
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| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" <head> <meta http-equiv= "Content-Type" content= "text/html; charset=UTF-8" /> <meta name= "description" content= "A short description." /> <meta name= "keywords" content= "put, keywords, here" /> <title>PHP-MySQL forum</title> <link rel= "stylesheet" href= "style.css" type= "text/css" > </head> <body> <h1>My forum</h1> <div id= "wrapper" > <div id= "menu" > <a class = "item" href= "/forum/index.php" >Home</a> - <a class = "item" href= "/forum/create_topic.php" >Create a topic</a> - <a class = "item" href= "/forum/create_cat.php" >Create a category</a> <div id= "userbar" > <div id= "userbar" >Hello Example. Not you? Log out.</div> </div> <div id= "content" > |
The attentive reader might have already noticed we're missing some things. There is no
</body>
or </html>
tag. They're in the footer.php page, as you can see below.
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| </div><!-- content --> </div><!-- wrapper --> <div id= "footer" >Created for Nettuts+</div> </body> </html> |
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| <?php $error = false; if ( $error = false) { //the beautifully styled content, everything looks good echo '<div id="content">some text</div>' ; } else { //bad looking, unstyled error :-( } ?> |
Another advantage is the possibility of making quick changes. You can see for yourself by editing the text in footer.php when you've finished this tutorial; you'll notice that the footer changes on every page immediately. Finally, we add a stylesheet which provides us with some basic markup - nothing too fancy.
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| body { background-color : #4E4E4E ; text-align : center ; /* make sure IE centers the page too */ } #wrapper { width : 900px ; margin : 0 auto ; /* center the page */ } #content { background-color : #fff ; border : 1px solid #000 ; float : left ; font-family : Arial ; padding : 20px 30px ; text-align : left ; width : 100% ; /* fill up the entire div */ } #menu { float : left ; border : 1px solid #000 ; border-bottom : none ; /* avoid a double border */ clear : both ; /* clear:both makes sure the content div doesn't float next to this one but stays under it */ width : 100% ; height : 20px ; padding : 0 30px ; background-color : #FFF ; text-align : left ; font-size : 85% ; } #menu a:hover { background-color : #009FC1 ; } #userbar { background-color : #fff ; float : right ; width : 250px ; } #footer { clear : both ; } /* begin table styles */ table { border-collapse : collapse ; width : 100% ; } table a { color : #000 ; } table a:hover { color : #373737 ; text-decoration : none ; } th { background-color : #B40E1F ; color : #F0F0F0 ; } td { padding : 5px ; } /* Begin font styles */ h 1 , #footer { font-family : Arial ; color : #F1F3F1 ; } h 3 { margin : 0 ; padding : 0 ;} /* Menu styles */ .item { background-color : #00728B ; border : 1px solid #032472 ; color : #FFF ; font-family : Arial ; padding : 3px ; text-decoration : none ; } .leftpart { width : 70% ; } .rightpart { width : 30% ; } . small { font-size : 75% ; color : #373737 ; } #footer { font-size : 65% ; padding : 3px 0 0 0 ; } .topic-post { height : 100px ; overflow : auto ; } .post-content { padding : 30px ; } textarea { width : 500px ; height : 200px ; } |
Step 3: Getting Ready for Action
Before we can read anything from our database, we need a connection. That's what connect.php is for. We'll include it in every file we are going to create.
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| <?php //connect.php $server = 'localhost' ; $username = 'usernamehere' ; $password = 'passwordhere' ; $database = 'databasenamehere' ; if (!mysql_connect( $server , $username , $password )) { exit ( 'Error: could not establish database connection' ); } if (!mysql_select_db( $database ) { exit ( 'Error: could not select the database' ); } ?> |
Step 4: Displaying the Forum Overview
Since we're just started with some basic techniques, we're going to make a simplified version of the forum overview for now.
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| <?php //create_cat.php include 'connect.php' ; include 'header.php' ; echo '<tr>' ; echo '<td class="leftpart">' ; echo '<h3><a href="category.php?id=">Category name</a></h3> Category description goes here' ; echo '</td>' ; echo '<td class="rightpart">' ; echo '<a href="topic.php?id=">Topic subject</a> at 10-10' ; echo '</td>' ; echo '</tr>' ; include 'footer.php' ; ?> |
Step 5: Signing up a User
Let's start by making a simple HTML form so that a new user can register.A PHP page is needed to process the form. We're going to use a $_SERVER variable. The $_SERVER variable is an array with values that are automatically set with each request. One of the values of the $_SERVER array is 'REQUEST_METHOD'. When a page is requested with GET, this variable will hold the value 'GET'. When a page is requested via POST, it will hold the value 'POST'. We can use this value to check if a form has been posted. See the signup.php page below.
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| <?php //signup.php include 'connect.php' ; include 'header.php' ; echo '<h3>Sign up</h3>' ; if ( $_SERVER [ 'REQUEST_METHOD' ] != 'POST' ) { /*the form hasn't been posted yet, display it note that the action="" will cause the form to post to the same page it is on */ echo '<form method= "post" action= "" > Username: <input type= "text" name= "user_name" /> Password: <input type= "password" name= "user_pass" > Password again: <input type= "password" name= "user_pass_check" > E-mail: <input type= "email" name= "user_email" > <input type= "submit" value= "Add category" /> </form>'; } else { /* so, the form has been posted, we'll process the data in three steps: 1. Check the data 2. Let the user refill the wrong fields (if necessary) 3. Save the data */ $errors = array (); /* declare the array for later use */ if (isset( $_POST [ 'user_name' ])) { //the user name exists if (!ctype_alnum( $_POST [ 'user_name' ])) { $errors [] = 'The username can only contain letters and digits.' ; } if ( strlen ( $_POST [ 'user_name' ]) > 30) { $errors [] = 'The username cannot be longer than 30 characters.' ; } } else { $errors [] = 'The username field must not be empty.' ; } if (isset( $_POST [ 'user_pass' ])) { if ( $_POST [ 'user_pass' ] != $_POST [ 'user_pass_check' ]) { $errors [] = 'The two passwords did not match.' ; } } else { $errors [] = 'The password field cannot be empty.' ; } if (! empty ( $errors )) /*check for an empty array, if there are errors, they're in this array (note the ! operator)*/ { echo 'Uh-oh.. a couple of fields are not filled in correctly..' ; echo '<ul>' ; foreach ( $errors as $key => $value ) /* walk through the array so all the errors get displayed */ { echo '<li>' . $value . '</li>' ; /* this generates a nice error list */ } echo '</ul>' ; } else { //the form has been posted without, so save it //notice the use of mysql_real_escape_string, keep everything safe! //also notice the sha1 function which hashes the password $sql = "INSERT INTO users(user_name, user_pass, user_email ,user_date, user_level) VALUES( '" . mysql_real_escape_string($_POST[' user_name ']) . "' , '" . sha1($_POST[' user_pass ']) . "' , '" . mysql_real_escape_string($_POST[' user_email ']) . "' , NOW(), 0)"; $result = mysql_query( $sql ); if (! $result ) { //something went wrong, display the error echo 'Something went wrong while registering. Please try again later.' ; //echo mysql_error(); //debugging purposes, uncomment when needed } else { echo 'Successfully registered. You can now <a href="signin.php">sign in</a> and start posting! :-)' ; } } } include 'footer.php' ; ?> |
- Validating the data
- If the data is not valid, show the form again
- If the data is valid, save the record in the database
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| INSERT INTO users(user_name, user_pass, user_email ,user_date, user_level) VALUES ( '" . mysql_real_escape_string($_POST[' user_name ']) . "' , '" . sha1($_POST[' user_pass ']) . "' , '" . mysql_real_escape_string($_POST[' user_email ']) . "' , NOW(), 0); |
"Never insert a plain password as-is. You MUST always encrypt it."Also, you can see that the function sha1() is used to encrypt the user's password. This is also a very important thing to remember. Never insert a plain password as-is. You MUST always encrypt it. Imagine a hacker who somehow manages to get access to your database. If he sees all the plain-text passwords he could log into any (admin) account he wants. If the password columns contain sha1 strings he has to crack them first which is almost impossible.
Note: it's also possible to use md5(), I always use sha1() because benchmarks have proved it's a tiny bit faster, not much though. You can replace sha1 with md5 if you like.
If the signup process was successful, you should see something like this:
Try refreshing your phpMyAdmin screen, a new record should be visible in the users table.
Step 6: Adding Authentication and User Levels
An important aspect of a forum is the difference between regular users and admins/moderators. Since this is a small forum and adding features like adding new moderators and stuff would take way too much time, we'll focus on the login process and create some admin features like creating new categories and closing a thread.Now that you've completed the previous step, we're going to make your freshly created account an admin account. In phpMyAdmin, click on the users table, and then 'Browse'. Your account will probably pop up right away. Click the edit icon and change the value of the user_level field from 0 to 1. That's it for now. You won't notice any difference in our application immediately, but when we've added the admin features a normal account and your account will have different capabilities.
The sign-in process works the following way:
- A visitor enters user data and submits the form
- If the username and password are correct, we can start a session
- If the username and password are incorrect, we show the form again with a message
The signin.php file is below. Don't think I'm not explaining what I'm doing, but check out the comments in the file. It's much easier to understand that way.
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| <?php //signin.php include 'connect.php' ; include 'header.php' ; echo '<h3>Sign in</h3>' ; //first, check if the user is already signed in. If that is the case, there is no need to display this page if (isset( $_SESSION [ 'signed_in' ]) && $_SESSION [ 'signed_in' ] == true) { echo 'You are already signed in, you can <a href="signout.php">sign out</a> if you want.' ; } else { if ( $_SERVER [ 'REQUEST_METHOD' ] != 'POST' ) { /*the form hasn't been posted yet, display it note that the action="" will cause the form to post to the same page it is on */ echo '<form method= "post" action= "" > Username: <input type= "text" name= "user_name" /> Password: <input type= "password" name= "user_pass" > <input type= "submit" value= "Sign in" /> </form>'; } else { /* so, the form has been posted, we'll process the data in three steps: 1. Check the data 2. Let the user refill the wrong fields (if necessary) 3. Varify if the data is correct and return the correct response */ $errors = array (); /* declare the array for later use */ if (!isset( $_POST [ 'user_name' ])) { $errors [] = 'The username field must not be empty.' ; } if (!isset( $_POST [ 'user_pass' ])) { $errors [] = 'The password field must not be empty.' ; } if (! empty ( $errors )) /*check for an empty array, if there are errors, they're in this array (note the ! operator)*/ { echo 'Uh-oh.. a couple of fields are not filled in correctly..' ; echo '<ul>' ; foreach ( $errors as $key => $value ) /* walk through the array so all the errors get displayed */ { echo '<li>' . $value . '</li>' ; /* this generates a nice error list */ } echo '</ul>' ; } else { //the form has been posted without errors, so save it //notice the use of mysql_real_escape_string, keep everything safe! //also notice the sha1 function which hashes the password $sql = "SELECT user_id, user_name, user_level FROM users WHERE user_name = '" . mysql_real_escape_string($_POST[' user_name ']) . "' AND user_pass = '" . sha1($_POST[' user_pass ']) . "' "; $result = mysql_query( $sql ); if (! $result ) { //something went wrong, display the error echo 'Something went wrong while signing in. Please try again later.' ; //echo mysql_error(); //debugging purposes, uncomment when needed } else { //the query was successfully executed, there are 2 possibilities //1. the query returned data, the user can be signed in //2. the query returned an empty result set, the credentials were wrong if (mysql_num_rows( $result ) == 0) { echo 'You have supplied a wrong user/password combination. Please try again.' ; } else { //set the $_SESSION['signed_in'] variable to TRUE $_SESSION [ 'signed_in' ] = true; //we also put the user_id and user_name values in the $_SESSION, so we can use it at various pages while ( $row = mysql_fetch_assoc( $result )) { $_SESSION [ 'user_id' ] = $row [ 'user_id' ]; $_SESSION [ 'user_name' ] = $row [ 'user_name' ]; $_SESSION [ 'user_level' ] = $row [ 'user_level' ]; } echo 'Welcome, ' . $_SESSION [ 'user_name' ] . '. <a href="index.php">Proceed to the forum overview</a>.' ; } } } } } include 'footer.php' ; ?> |
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| SELECT user_id, user_name, user_level FROM users WHERE user_name = '" . mysql_real_escape_string($_POST[' user_name ']) . "' AND user_pass = '" . sha1($_POST[' user_pass']) |
If the user is signed in successfully, we're doing a few things:
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| <?php //set the $_SESSION['signed_in'] variable to TRUE $_SESSION [ 'signed_in' ] = true; //we also put the user_id and user_name values in the $_SESSION, so we can use it at various pages while ( $row = mysql_fetch_assoc( $result )) { $_SESSION [ 'user_id' ] = $row [ 'user_id' ]; $_SESSION [ 'user_name' ] = $row [ 'user_name' ]; } ?> |
Of course signing in requires another function, signing out! The sign-out process is actually a lot easier than the sign-in process. Because all the information about the user is stored in $_SESSION variables, all we have to do is unset them and display a message.
Now that we've set the $_SESSION variables, we can determine if someone is signed in. Let's make a last simple change to header.php:
Replace:
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| < div id = "userbar" >Hello Example. Not you? Log out.</ div > |
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| <?php <div id= "userbar" > if ( $_SESSION [ 'signed_in' ]) { echo 'Hello' . $_SESSION [ 'user_name' ] . '. Not you? <a href="signout.php">Sign out</a>' ; } else { echo '<a href="signin.php">Sign in</a> or <a href="sign up">create an account</a>.' ; } </div> |
Step 7: Creating a Category
We want to create categories so let's start with making a form.
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| < form method = "post" action = "" > Category name: < input type = "text" name = "cat_name" /> Category description: < textarea name = "cat_description" /></ textarea > < input type = "submit" value = "Add category" /> </ form > |
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| <?php //create_cat.php include 'connect.php' ; if ( $_SERVER [ 'REQUEST_METHOD' ] != 'POST' ) { //the form hasn't been posted yet, display it echo '<form method=' post ' action=' '> Category name: <input type= 'text' name= 'cat_name' /> Category description: <textarea name= 'cat_description' /></textarea> <input type= 'submit' value= 'Add category' /> </form>'; } else { //the form has been posted, so save it $sql = ìINSERT INTO categories(cat_name, cat_description) VALUES( '' . mysql_real_escape_string( $_POST [ 'cat_name' ]) . ì', '' . mysql_real_escape_string( $_POST [ 'cat_description' ]) . ì ')' ; $result = mysql_query( $sql ); if (! $result ) { //something went wrong, display the error echo 'Error' . mysql_error(); } else { echo 'New category successfully added.' ; } } ?> |
Step 8: Adding Categories to index.php
We've created some categories, so now we're able to display them on the front page. Let's add the following query to the content area of index.php.
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| SELECT categories.cat_id, categories.cat_name, categories.cat_description, FROM categories |
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| <?php //create_cat.php include 'connect.php' ; include 'header.php' ; $sql = "SELECT cat_id, cat_name, cat_description, FROM categories"; $result = mysql_query( $sql ); if (! $result ) { echo 'The categories could not be displayed, please try again later.' ; } else { if (mysql_num_rows( $result ) == 0) { echo 'No categories defined yet.' ; } else { //prepare the table echo '<table border= "1" > <tr> <th>Category</th> <th>Last topic</th> </tr>'; while ( $row = mysql_fetch_assoc( $result )) { echo '<tr>' ; echo '<td class="leftpart">' ; echo '<h3><a href="category.php?id">' . $row [ 'cat_name' ] . '</a></h3>' . $row [ 'cat_description' ]; echo '</td>' ; echo '<td class="rightpart">' ; echo '<a href="topic.php?id=">Topic subject</a> at 10-10' ; echo '</td>' ; echo '</tr>' ; } } } include 'footer.php' ; ?> |
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| category.php?cat_id=23 |
Step 9: Creating a Topic
In this step, we're combining the techniques we learned in the previous steps. We're checking if a user is signed in, we'll use an input query to create the topic and create some basic HTML forms.The structure of create_topic.php can hardly be explained in a list or something, so I rewrote it in pseudo-code.
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| <?php if (user is signed in) { //the user is not signed in } else { //the user is signed in if (form has not been posted) { //show form } else { //process form } } ?> |
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| <?php //create_cat.php include 'connect.php' ; include 'header.php' ; echo '<h2>Create a topic</h2>' ; if ( $_SESSION [ 'signed_in' ] == false) { //the user is not signed in echo 'Sorry, you have to be <a href="/forum/signin.php">signed in</a> to create a topic.' ; } else { //the user is signed in if ( $_SERVER [ 'REQUEST_METHOD' ] != 'POST' ) { //the form hasn't been posted yet, display it //retrieve the categories from the database for use in the dropdown $sql = "SELECT cat_id, cat_name, cat_description FROM categories"; $result = mysql_query( $sql ); if (! $result ) { //the query failed, uh-oh :-( echo 'Error while selecting from database. Please try again later.' ; } else { if (mysql_num_rows( $result ) == 0) { //there are no categories, so a topic can't be posted if ( $_SESSION [ 'user_level' ] == 1) { echo 'You have not created categories yet.' ; } else { echo 'Before you can post a topic, you must wait for an admin to create some categories.' ; } } else { echo '<form method= "post" action= "" > Subject: <input type= "text" name= "topic_subject" /> Category:'; echo '<select name="topic_cat">' ; while ( $row = mysql_fetch_assoc( $result )) { echo '<option value="' . $row [ 'cat_id' ] . '">' . $row [ 'cat_name' ] . '</option>' ; } echo '</select>' ; echo 'Message: <textarea name= "post_content" /></textarea> <input type= "submit" value= "Create topic" /> </form>'; } } } else { //start the transaction $query = "BEGIN WORK;" ; $result = mysql_query( $query ); if (! $result ) { //Damn! the query failed, quit echo 'An error occured while creating your topic. Please try again later.' ; } else { //the form has been posted, so save it //insert the topic into the topics table first, then we'll save the post into the posts table $sql = "INSERT INTO topics(topic_subject, topic_date, topic_cat, topic_by) VALUES( '" . mysql_real_escape_string($_POST[' topic_subject ']) . "' , NOW(), " . mysql_real_escape_string($_POST['topic_cat']) . " , " . $_SESSION['user_id'] . " )"; $result = mysql_query( $sql ); if (! $result ) { //something went wrong, display the error echo 'An error occured while inserting your data. Please try again later.' . mysql_error(); $sql = "ROLLBACK;" ; $result = mysql_query( $sql ); } else { //the first query worked, now start the second, posts query //retrieve the id of the freshly created topic for usage in the posts query $topicid = mysql_insert_id(); $sql = "INSERT INTO posts(post_content, post_date, post_topic, post_by) VALUES ( '" . mysql_real_escape_string($_POST[' post_content ']) . "' , NOW(), " . $topicid . " , " . $_SESSION['user_id'] . " )"; $result = mysql_query( $sql ); if (! $result ) { //something went wrong, display the error echo 'An error occured while inserting your post. Please try again later.' . mysql_error(); $sql = "ROLLBACK;" ; $result = mysql_query( $sql ); } else { $sql = "COMMIT;" ; $result = mysql_query( $sql ); //after a lot of work, the query succeeded! echo 'You have successfully created <a href="topic.php?id=' . $topicid . '">your new topic</a>.' ; } } } } } include 'footer.php' ; ?> |
Showing the form
We're starting with a simple HTML form. There is actually something special here, because we use a dropdown. This dropdown is filled with data from the database, using this query:
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| SELECT cat_id, cat_name, cat_description FROM categories |
Processing the form
The process of saving the topic consists of two parts: saving the topic in the topics table and saving the first post in the posts table. This requires something quite advanced that goes a bit beyond the scope of this tutorial. It's called a transaction, which basically means that we start by executing the start command and then rollback when there are database errors and commit when everything went well. More about transactions.
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| <?php //start the transaction $query = "BEGIN WORK;" ; $result = mysql_query( $query ); //stop the transaction $sql = "ROLLBACK;" ; $result = mysql_query( $sql ); //commit the transaction $sql = "COMMIT;" ; $result = mysql_query( $sql ); ?> |
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| INSERT INTO topics(topic_subject, topic_date, topic_cat, topic_by) VALUES ( '" . mysql_real_escape_string($_POST[' topic_subject ']) . "' , NOW(), " . mysql_real_escape_string($_POST['topic_cat']) . " , " . $_SESSION['user_id'] . " ) |
If the query executed without errors we proceed to the second query. Remember we are still doing a transaction here. If we would've got errors we would have used the ROLLBACK command.
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| INSERT INTO posts(post_content, post_date, post_topic, post_by) VALUES ( '" . mysql_real_escape_string($_POST[' post_content ']) . "' , NOW(), " . $topicid . " , " . $_SESSION['user_id'] . " ) |
Then the post is inserted into the posts table. This query looks a lot like the topics query. The only difference is that this post refers to the topic and the topic referred to a category. From the start, we decided to create a good data model and here is the result: a nice hierarchical structure.
Step 10: Category View
We're going to make an overview page for a single category. We've just created a category, it would be handy to be able to view all the topics in it. First, create a page called category.php.A short list of the things we need:
Needed for displaying the category
- cat_name
- cat_description
- topic_id
- topic_subject
- topic_date
- topic_cat
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| SELECT cat_id, cat_name, cat_description FROM categories WHERE cat_id = " . mysql_real_escape_string($_GET[ 'id' ]) |
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| SELECT topic_id, topic_subject, topic_date, topic_cat FROM topics WHERE topic_cat = " . mysql_real_escape_string($_GET[ 'id' ]) |
The complete code of category.php will be the following:
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| <?php //create_cat.php include 'connect.php' ; include 'header.php' ; //first select the category based on $_GET['cat_id'] $sql = "SELECT cat_id, cat_name, cat_description FROM categories WHERE cat_id = " . mysql_real_escape_string( $_GET [ 'id' ]); $result = mysql_query( $sql ); if (! $result ) { echo 'The category could not be displayed, please try again later.' . mysql_error(); } else { if (mysql_num_rows( $result ) == 0) { echo 'This category does not exist.' ; } else { //display category data while ( $row = mysql_fetch_assoc( $result )) { echo '<h2>Topics in ′' . $row [ 'cat_name' ] . '′ category</h2>' ; } //do a query for the topics $sql = "SELECT topic_id, topic_subject, topic_date, topic_cat FROM topics WHERE topic_cat = " . mysql_real_escape_string( $_GET [ 'id' ]); $result = mysql_query( $sql ); if (! $result ) { echo 'The topics could not be displayed, please try again later.' ; } else { if (mysql_num_rows( $result ) == 0) { echo 'There are no topics in this category yet.' ; } else { //prepare the table echo '<table border= "1" > <tr> <th>Topic</th> <th>Created at</th> </tr>'; while ( $row = mysql_fetch_assoc( $result )) { echo '<tr>' ; echo '<td class="leftpart">' ; echo '<h3><a href="topic.php?id=' . $row [ 'topic_id' ] . '">' . $row [ 'topic_subject' ] . '</a><h3>' ; echo '</td>' ; echo '<td class="rightpart">' ; echo date ( 'd-m-Y' , strtotime ( $row [ 'topic_date' ])); echo '</td>' ; echo '</tr>' ; } } } } } include 'footer.php' ; ?> |
Step 11: Topic View
The SQL queries in this step are complicated ones. The PHP-part is all stuff that you've seen before. Let's take a look at the queries. The first one retrieves basic information about the topic:
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| SELECT topic_id, topic_subject FROM topics WHERE topics.topic_id = " . mysql_real_escape_string($_GET[ 'id' ]) |
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| SELECT posts.post_topic, posts.post_content, posts.post_date, posts.post_by, users.user_id, users.user_name FROM posts LEFT JOIN users ON posts.post_by = users.user_id WHERE posts.post_topic = " . mysql_real_escape_string($_GET[ 'id' ]) |
The final topic view looks like this:
Step 12: Adding a Reply
Let's create the last missing part of this forum, the possibility to add a reply. We'll start by creating a form:
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| < form method = "post" action = "reply.php?id=5" > < textarea name = "reply-content" ></ textarea > < input type = "submit" value = "Submit reply" /> </ form > |
The complete reply.php code looks like this.
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| <?php //create_cat.php include 'connect.php' ; include 'header.php' ; if ( $_SERVER [ 'REQUEST_METHOD' ] != 'POST' ) { //someone is calling the file directly, which we don't want echo 'This file cannot be called directly.' ; } else { //check for sign in status if (! $_SESSION [ 'signed_in' ]) { echo 'You must be signed in to post a reply.' ; } else { //a real user posted a real reply $sql = "INSERT INTO posts(post_content, post_date, post_topic, post_by) VALUES ( '" . $_POST[' reply-content '] . "' , NOW(), " . mysql_real_escape_string($_GET['id']) . " , " . $_SESSION['user_id'] . " )"; $result = mysql_query( $sql ); if (! $result ) { echo 'Your reply has not been saved, please try again later.' ; } else { echo 'Your reply has been saved, check out <a href="topic.php?id=' . htmlentities( $_GET [ 'id' ]) . '">the topic</a>.' ; } } } include 'footer.php' ; ?> |
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