Php session

Sessions
A session begins when a visiting client somehow identifies itself to the web server.
The web server assigns the client a unique session id, which the client uses to re-identify
itself as it moves from page to page on the website. Most of the time, these
unique ids are stored in session cookies that expire after the client hasn't interacted
with the server for some amount of time. The amount of time varies depending on
the web application. For example, an online investment site might have very short
sessions, so that if a user leaves her computer without logging out, another user who
sits down at the same computer several minutes later cannot continue with the first
user's session.
Configuring Sessions
In PHP, session management is configured in the php.ini file. To have a user's session
start as soon as the user visits the website, the session.auto_start flag must be set to 1.
The session length is also set in the php.ini file with the session.gc_maxlifetime
variable. The default value is 1440 seconds (24 minutes).

Session Functions
Function Explanation
session_start()
Starts new session if one
does not exist. Continues
current session if one exists.
session_unset() Unsets all session variables.
session_destroy() Kills session.
Ex 1.
<?php
//Begin a session and create a session variable in
//the $_SESSION array.
session_start();
$_SESSION['Greeting'] = 'Hello world!';
echo $_SESSION['Greeting'];
?>
<hr>
<a href="Session2.php">Next page</a>

Ex 2.
<?php
//Continue session, show that session variable still
//exists and then unset the session variable
session_start();
unset($_SESSION['Greeting']);
?>
<a href="Session3.php">Next page</a>
Ex 3.
<?php
//Continue session, show that session variable no longer
//exists and then kill session.
session_start();
session_unset();
session_destroy();
?>

Cookies
Cookies are stored in text files that sit on the client machine. Web pages with the
right permissions can read from and write to cookies. They are generally used to
track user information between visits.
In PHP, cookies are set with the setcookie() function, which can take several
parameters including:
The cookie's name (required).
The cookie's value.
The cookie's expiration date (if this isn't set, the cookie will expire when the
browser window is closed).
The directory path on the server that can read the cookie.
The domain name that can read the cookie.
A flag indicating whether the cookie should only be read over https.

Create a Cookie?
The setcookie() function is used to set a cookie.
Note: The setcookie() function must appear BEFORE the <html> tag.
Syntax
setcookie(name, value, expire, path, domain);
Example 1
In the example below, we will create a cookie named "user" and assign the value
"Alex Porter" to it. We also specify that the cookie should expire after one hour:
< ?php
setcookie("user", "Alex Porter", time()+3600);
?>
< html>
.....
Note: The value of the cookie is automatically URLencoded when sending the
cookie, and automatically decoded when received (to prevent URLencoding, use
setrawcookie() instead).

Retrieve a Cookie Value?
The PHP $_COOKIE variable is used to retrieve a cookie value.
In the example below, we retrieve the value of the cookie named "user" and display
it on a page:
< ?php
// Print a cookie
echo $_COOKIE["user"];
// A way to view all cookies
print_r($_COOKIE);
?>
In the following example we use the isset() function to find out if a cookie has been
set:
< html>
< body>
< ?php
if (isset($_COOKIE["user"]))
echo "Welcome " . $_COOKIE["user"] . "!<br>";
else
echo "Welcome guest!<br>";
?>
< /body>
< /html>

PHP Simple E-Mail
The simplest way to send an email with PHP is to send a text email.
In the example below we first declare the variables ($to, $subject, $message,
$from, $headers), then we use the variables in the mail() function to send an
e-mail:
< ?php
$to = "someone@example.com";
$subject = "Test mail";
$message = "Hello! This is a simple email message.";
$from = "someonelse@example.com";
$headers = "From:" . $from;
mail($to,$subject,$message,$headers);
echo "Mail Sent.";
?>

PHP Mail Form
With PHP, you can create a feedback-form on your website. The example below
sends a text message to a specified e-mail address:
< html>
< body>
< ?php
if (isset($_REQUEST['email']))
//if "email" is filled out, send email
{
//send email
$email = $_REQUEST['email'] ;
$subject = $_REQUEST['subject'] ;
$message = $_REQUEST['message'] ;
mail("someone@example.com", $subject,
$message, "From:" . $email);
echo "Thank you for using our mail form";
}

else
//if "email" is not filled out, display the form
{
echo "<form method='post' action='mailform.php'>
Email: <input name='email' type='text'><br>
Subject: <input name='subject' type='text'><br>
Message:<br>
<textarea name='message' rows='15' cols='40'>
</textarea><br>
<input type='submit'>
</form>";
}
?>
< /body>
< /html>

What is an Exception
With PHP 5 came a new object oriented way of dealing with errors.
Exception handling is used to change the normal flow of the code execution if a
specified error (exceptional) condition occurs. This condition is called an
exception.
This is what normally happens when an exception is triggered:
The current code state is saved
The code execution will switch to a predefined (custom) exception handler
function
Depending on the situation, the handler may then resume the execution from
the saved code state, terminate the script execution or continue the script from a
different location in the code
We will show different error handling methods:
Basic use of Exceptions
Creating a custom exception handler
Multiple exceptions
Re-throwing an exception
Setting a top level exception handler

Use of Exceptions
When an exception is thrown, the code following it will not be executed, and PHP
will try to find the matching "catch" block.
If an exception is not caught, a fatal error will be issued with an "Uncaught
Exception" message.
Lets try to throw an exception without catching it:
< ?php
//create function with an exception
function checkNum($number)
{
if($number>1)
{
throw new Exception("Value must be 1 or below");
}
return true;
}
//trigger exception
checkNum(2);
?>

Databases Connection
A database is a collection of information / data that is organized so that it can
easily be retrieved, administrated and updated. Databases thereby enable the
opportunity to create dynamic websites with large amounts of information. For
example, all data on members of argus.net and all posts in the forums are stored
in databases.
There are many different databases: MySQL, MS Access, MS SQL Server, Oracle
SQL Server and many others. In this tutorial, we will use the MySQL database.
MySQL is the natural place to start when you want to use databases in PHP.
If you have a hosted website with PHP, MySQL is probably already installed on
the server.
If you use XAMPP MySQL is already installed and ready to use on your computer.
Just make sure MySQL is running in the Control Panel:

In the rest of this lesson, we will look more closely at how you connect to your
database server, before we learn to create databases and retrieve and update data
in the following sessions.

Connection to database server
First, you need to have access to the server where your MySQL database is
located. This is done with the function mysql_connect with the following syntax:
mysql_connect(server, username, password)
Example of a MySQL connection with XAMPP (default settings):
mysql_connect("localhost", "root", "") or die (mysql_error());
Create database and tables with phpMyAdmin
It can be useful to be able to create databases and tables directly in PHP. But
often, it will be easier to use phpMyAdmin (or any other MySQL administration
tool), which is standard on most web hosts and XAMPP. The screendumps below
shows how to create a database and tables in phpMyAdmin.
Start by logging onto phpMyAdmin. Often, the address will be the same as your
MySQL server (eg. "http://mysql.myhost.com") and with the same username and
password. In XAMPP, the address is http://localhost/phpmyadmin/.
When you are logged on, simply type a name for the database and press the
button "Create":

At some hosts, it's possible the have already created a database, and you may
not have the rights to create more. If that is the case, you obviously just use the
assigned database.
To create a table, click on the tab "Databases" and choose a database by
clicking on it:

Then there will be a box titled "Create new table in database", where you type
the name of the table and the number of columns and press the button "Go":

Then you can name the columns and set the data type, etc.,
Insert data using SQL
You use MySQL to insert data in a database in the same way that you can use SQL
to create databases and tables. The syntax of the MySQL query is:
INSERT INTO TableName(column1, column2, ...) VALUES(value1, value2, ...)

Get data from database
The MySQL query returns a result in the form of a series of records. These
records are stored in a so-called recordset. A recordset can be described as a kind
of table in the server's memory, containing rows of data (records), and each
record is subdivided into individual fields (or columns).
A recordset can be compared to a table where each record could be compared to a
row in the table. In PHP, we can run through a recordset with a loop and the
function mysql_fetch_array, which returns each row as an array.
The code below shows how to use mysql_fetch_array to loop through a recordset:
<html>
<head> <title>Retrieve data from database </title> </head>
<body>
<?php
// Connect to database server
mysql_connect("mysql.myhost.com", "user", "sesame") or die (mysql_error ());
// Select database
mysql_select_db("mydatabase") or die(mysql_error());
// SQL query
$strSQL = "SELECT * FROM people";
// Execute the query (the recordset $rs contains the result)
$rs = mysql_query($strSQL);

// Loop the recordset $rs
// Each row will be made into an array ($row) using mysql_fetch_array
while($row = mysql_fetch_array($rs))
{
// Write the value of the column FirstName (which is now in the array $row)
echo $row['FirstName'] . "<br />";
}
// Close the database connection
mysql_close();
?>
</body>
</html>

Delete a record
When deleting a record, you can use the unique AutoNumber field in the
database. In our database, it is the column named id. Using this unique
identifier ensures that you only delete one record. In the next example, we delete
the record where id has the value 24:
<html>
<head> <title>Delete data in the database</title> </head>
<body>
<?php
// Select database
// The SQL statement that deletes the record
$strSQL = "DELETE FROM people WHERE id = 24";
mysql_query($strSQL);
mysql_close();
?>
<h1>Record is deleted!</h1>
</body> </html>

Update cells in the table "people“
The code below updates Donald Duck's first name to D. and changes the phone
number to 44444444. The other information (last name and birthdate) are not
changed. You can try to change the other people's data by writing your own SQL
statements.
<html>
<head> <title>Update data in database</title> </head> <body>
<?php
// Select database
// The SQL statement is built
$strSQL = "Update people set ";
$strSQL = $strSQL . "FirstName= 'D.', ";
$strSQL = $strSQL . "Phone= '44444444' ";
$strSQL = $strSQL . "Where id = 22";
// The SQL statement is executed
mysql_query($strSQL);
mysql_close();
?>
<h1>The database is updated!</h1> </body> </html>

Php session

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Php session