In this post we are going to expand the Note
Keeping Application, using MySQL
to create a complete multi-user Application which would be able to register
new users as well. It’d be a multi-user system hence many users
can register and work on their notes simultaneously. Each user’s data
will be private to them. It’d also have the missing features such as editing
and deleting of existing notes, hence a complete Note Keeping Application.
In a multi-user application we need to separate each user’s data so that
every user is shown only the data belonging to them. As we’ll be using
MySQL database to store data, one option is to create a table for each user,
it’d be good but when you have like thousands of users, having a table
for each is not very efficient.
There is one very efficient technique however, to separate data of different
users using relational database structure. For this we’ll only need two
tables for the whole application. One will store user-data along with an unique
userID (serialized) for each row (or user). The second table will store note
data, such as serial number, title, body etc. along with one more column to
store the userID (from table 1) to know the user storing the note. The following
image will clarify this:
ID field was a Primary
Key in the first table while when it appears in the second table to
make relation between the two tables; it is called a ‘foreign key’.
Please note that we are not doing anything special to create a foreign key,
just using a logical relation.
So with this structure any note getting stored has a valid ID (according to
the user who is logged in) in the userID field of the second (notes) table.
Thus each row in the second table is logically separated and related with the
user who has stored it.
Apart from multi-user functionality, we’re also integrating other features
like editing and deleting existing notes, which are done using the following
SQL
queries:
For editing a note:
UPDATE <table-name> SET <column1=new-data1>,
<column2=new-data2>,
…
WHERE <column0=some-data>
For deleting a note:
DELETE FROM <table-name>
WHERE <some-column=some-data>
Now we have enough knowledge to see the code:
login.php:
<html>
<head>
<title>My Notes | Login</title>
</head>
<body>
<h1>My Notes</h1>
<h2>Login </h2>
<?php
//if submit button was pressed
//that means form was submitted
if(isset($_POST[submit]))
{
//connect to MySQL
//change -USER- and -PASS-
$db=new mysqli(localhost,-USER-,-PASS-);
$db->select_db(one);
//fetch other form data
$username=trim($_POST[username]);
$password=trim($_POST[password]);
//start a session
session_start();
$result=$db->query("select pass from user where uname=$username");
if($result->num_rows>0)
{
$pass=$result->fetch_row();
$pass=$pass[0];
if($password=$pass)
{
//save session variable with the username
//which will be unique
$_SESSION[user]=$username;
//redirect to homepage
header("Location: home.php");
}
}
echo "<p style="color:#ff0000;">Incorrect Username/Password. Please Try Again.</p>";
//close db connection
$db->close();
}
else
//requesting the login page
{
//if requesting the login page
//check if already logged in
//and redirect to homepage if true
//start session
session_start();
if(isset($_SESSION[user]))
{
//redirect to homepage
//if already logged in
header("Location: home.php");
}
}
//if not logged in show the login page
?>
<form name="form1" id="form1" method="post" action="">
<table width="30%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td>Username</td>
<td><input name="username" type="text" id="username" /></td>
</tr>
<tr>
<td>Password</td>
<td><input name="password" type="password" id="password" /></td>
</tr>
<tr>
<td> </td>
<td><input name="submit" type="submit" id="submit" value="Submit" /></td>
</tr>
</table>
</form>
<p>New User <a href="user_reg.php">Register Here</a></p>
</body>
</html>
user_reg.php: Please see Designing
a User-Registration Script in PHP for this. Since this post has already
gotten so long.
home.php:
<html>
<head>
<title>My Notes</title>
</head>
<body>
<h1>My Notes</h1>
<p>Create A New Note</p>
<form name="form1" id="form1" method="post" action="home.php">
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="22%"><font size="2">Title</font></td>
<td width="78%"><input name="title" type="text" id="title" size="30" /></td>
</tr>
<tr>
<td><font size="2">Body</font></td>
<td><textarea name="body" cols="30" rows="7" id="body"></textarea></td>
</tr>
<tr>
<td><input name="post" type="submit" id="post" value="Post Note" /></td>
<td><input type="reset" name="Submit2" value="Reset" /></td>
</tr>
</table>
</form>
<?php
//start session again
session_start();
//store the username
//that was stored by the login page
$uname=$_SESSION[user];
//if someone is requesting this page
//without logging in
if(!isset($uname))
//redirect to login page
header(Location: login.php);
//connect to MySQL
//provide your USERNAME and PASSWORD
//change localhost to the MySQL server
//host, if not using on local server
$db=new mysqli(localhost,root,26519877);
//if this is the first time
//and database is not craeted
if(!$db->select_db(one))
//create the database
$db->query(create database one);
//select the databasw to work with
$db->select_db(one);
//if table is not craeted, craete it
if(!$db->query(select * from notes))
$db->query(create table notes(id int auto_increment primary key, title varchar(100), date varchar(50), body varchar(1000), userid int));
//find the userid from the user table
//it is the unique id of the logged in user
//itd be needed to retrieve and save notes
$result=$db->query("select userid from user where uname=$uname");
$result=$result->fetch_row();
$userid=$result[0];
//if logged in
echo "<p style="background: #000; color: #fff;"><b>Hello: <i>".$_SESSION[user]."</b></i></p>";
echo "<a href="?action=logout">Log Out</a></p>";
//----PERFORM ACTION AS PER WHAT WAS CLICKED----
//if post button was pressed
//i.e note was posted
if(isset($_POST[post]))
{
$title=strip_tags($_POST[title]);
$body=strip_tags($_POST[body]);
//convert newlines in the body to <br />
//so that formatting dont by user remains
$body=nl2br($body);
//have current date and time
$date=date(H:iA jS F Y);
//escape special characters that
//can cause probs with MySQL
$title=addslashes($title);
$body=addslashes($body);
$date=addslashes($date);
//if body or title field was not blank
if($body!= && $title!=)
//ready to insert data
$db->query("insert into notes (title, date, body, userid) values ($title, $date, $body, $userid)");
}
//if edit button was clicked on from the edit
//page
if(isset($_POST[edit]))
{
$title=strip_tags($_POST[title]);
$body=strip_tags($_POST[body]);
$date=strip_tags($_POST[date]);
//fetch the Note ID sent by the hiddeen form element
$id=trim($_POST[id]);
//convert newlines in the body to <br />
//so that formatting dont by user remains
$body=nl2br($body);
//have current date and time
//escape special characters that
//can cause probs with MySQL
$title=addslashes($title);
$body=addslashes($body);
$date=addslashes($date);
//if body or title field was not blank
if($body!= && $title!=)
//ready to updatedata
$db->query("update notes set title=$title, date=$date, body=$body where id=$id");
}
//if delete link is clicked w.r.t any note
if($_GET[action]==del)
{
//have the ID of note to be deleted
$noteid=$_GET[id];
$db->query("delete from notes where id=$noteid");
}
//if logout was clicked
if($_GET[action]==logout)
{
unset($_SESSION[user]);
//redirect to login page
header(Location: login.php);
}
//----/ACTION PERFORMED----
//----SHOW THE PREVIOUS NOTES----
echo "<h2 style="background: #000; color: #fff;">Previous Notes</h2>";
//fetch all the notes of the user
//order by id desc to have in newest first order
$result=$db->query("select * from notes where userid=$userid order by id desc");
$num_rows=$result->num_rows;
for($i=0;$i<$num_rows;$i++)
{
$row=$result->fetch_row();
$id=$row[0];
$title=$row[1];
$date=$row[2];
$body=$row[3];
//wed escaped special chars
//so de-escaping those
$title=stripslashes($title);
$body=stripslashes($body);
$date=stripslashes($date);
echo "<h3>$title</h3>
<p><i>$date</i></p>
<p>$body<br />";
//echo deleting option
echo "<a href="?action=del&id=$id">Delete</a> | <a href="edit.php?id=$id">Edit</a></p>";
}
//----/NOTES SHOWN----
$db->close();
?>
</body>
</html>
edit.php:
<?php
//fetch the unique note id sent
$id=(int)$_GET[id];
//start session again
session_start();
//store the username
//that was stored by the login page
$uname=$_SESSION[user];
//if someone is requesting this page
//without logging in
if(!isset($uname))
//redirect to login page
header(Location: login.php);
//connect to MySQL
//provide your USERNAME and PASSWORD
//change localhost if required
$db=new mysqli(localhost,root,26519877);
//select the databasw to work with
$db->select_db(one);
//query MySQL for the specific note
$result=$db->query("select * from notes where id=$id");
//there will only be one note with an id
//fetch the row and its data
$result=$result->fetch_row();
$title=$result[1];
$date=$result[2];
$body=$result[3];
$db->close();
?>
<html>
<head>
<title>My Notes | Edit</title>
</head>
<body>
<h1>My Notes</h1>
<p>Edit Note</p>
<form name="form1" id="form1" method="post" action="home.php">
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="22%"><font size="2">Title</font></td>
<td width="78%"><input name="title" type="text" id="title" value="<?php echo $title; ?>" size="30" /></td>
</tr>
<td>Date</td>
<td><input name="date" type="text" id="date" value="<?php echo $date; ?>" size="30">
<!-- hidden field is used for sending some information that user doesnt need to edit -->
<!--here we are using it to send the ID of the note, it is needed to UPDATE the row -->
<input name="id" type="hidden" id="id" value="<?php echo $id; ?>"></td>
<tr>
<td><font size="2">Body</font></td>
<td><textarea name="body" cols="30" rows="7" id="body"><?php echo $body; ?></textarea></td>
</tr>
<tr>
<td><input name="edit" type="submit" id="edit" value="Save Changes" /></td>
<td><input type="reset" name="Submit2" value="Reset" /></td>
</tr>
<tr>
</tr>
</table>
</form>
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