PHP ~ AboutLearning

PHP is a server-side scripting language. means that the script is run on web browser and not on users browser. Therefore there is no need to worry about compatibility issues. PHP is comparatively new language unlike Perl (CGI) and Java). PHP is becoming one of the most popular scripting language on the internet.

PHP Install
Since we know that PHP is a server side scripting language, there is no need for your users to install new software, your web host will need to have PHP setup on their server.

How to install PHP?

IF PHP is supported by your server then you need not do anything. You need not to compile anything or install any extra tools. just create your php files and save them in your web directory. Then server will parse them.

And if PHP is not supported by the server, you should install it. Here is a link to a good tutorial from PHP.net on how to install PHP5:

http://www.php.net/manual/en/install.php

Download PHP

Download PHP for free here: http://www.php.net/downloads.php

Download MySQL Database

Download MySQL for free here: http://www.mysql.com/downloads/index.html

Download Apache Server

Download Apache for free here: http://httpd.apache.org/download.cgi

General Syntax for PHP

PHP scripts should always be enclosed in between two PHP tags. This tells the server to parse all the information between them as PHP code. The three different ways for this are as follows:

<?
Here is a PHP Code
?>

<?php
Here is a PHP Code
php?>

Your First PHP Script

You will be writing very basic code as your first PHP script. All that it will do is, just print out all the information about PHP on your server. Write following code in your text editor:

<?
phpinfo();
?>

Nearly all lines are ended with a semicolon as with many other scripting and programming languages and if you miss it you will get an error.

Finishing and Testing the PHP Script

After writing your script save it as phpinfo.php and then upload it to your server. in the normal way. And now, using your browser, go to the URL of the script. If it has worked (and if PHP is installed on your server) you will get a huge page containing all the information about PHP on your server

PHP Variables

As with any other programming languages, PHP allows to define variables. In PHP there are many variable types,but the most common among them is a String variable.
As with any other programming languages, PHP allows to define variables. In PHP there are many variable types, but the most common among them is a String variable.

String Variable

A String variable holds text and numbers. All strings begin with a symbol "$". To assign some text to the string you can use the following code:

$welcome_text = "Hello and welcome to VYOM Technosoft";

Strings are case sensetive so the string variable $Welcome_Text is not the same as $welcome_text A string name can contain letters, underscores and numbers. but it should not begin with a number or underscore. When assigning numbers to the string variables you need not include the quotes so:

$user_id = 987
would be allowed.

How to display the Variable.

We use exactly the same code to display a variable on the screen, as we used to display the text. But slightly different form. The following code would display the welcome text:

<?
$welcome_text = "Hello and welcome to VYOM Technosoft";
print($welcome_text);
?>

As you can see, the only major difference is that you need not put the quotation marks if you are printing a variable.

How to format the Text?

Output from your PHP programs is quite boring unfortunately. All the content is just output in the browser's default font. It is easy, to format your text using HTML. This is because, as we know that the PHP is a server side scripting language, code is been executed before the page is sent to browser. This means, only the resulting information from script is sent, so in the above example, the browser would just sent the text:

Hello and welcome to VYOM Technosoft

This means, that you can include standard HTML markup in your strings and scripts. The problem with this is that many HTML tags require the " symbol. You may notice that this symbol will clash with the quotation marks used to print the text. To overcome this confusion you must tell the script which quotes to be used (those at the beginning and end of the output) and which to be ignored (those of the HTML code).

How to solve this problem?

To illustrate this let us consider the example, Change the font of the text to the Arial font in red. The code for this is as follows.

As you can see this code contains 4 quotation marks so can confuse the script. To solve this you must add a backslash before each quotation mark to make the PHP script ignore it. Then the code would look like.

Now you can include this in your print statement,which will make the browser display it.

print("<font face=\"Arial\" color\"#FF0000\">Hello and welcome </font>");
Output:Hello and welcome

PHP Operators

Operator is a symbol or can be a series of symbols, which when used .with some values performs some action and produce a new value

Assignment Operator

Assignment operator "=" is most widely used operator in PHP. This operator is used to initialize the variable.This operator is used in between two operands. It evaluates right-hand operand and assigs its value to the left-hand operand. Most operators are used to produce some result without changing the value of their operands. But assignment operator breaks this rule.

print ($name = “John”); //assigns “John” to “$name”, then
outputs “$name”

At the same time you can perform multiple things. So you can assign not only the word “John” to the variable “$name”, but can also output the variable at (almost) the same time..

Dot Operator

Using the concatenation operator we can append additional characters to a string. This is a single dot “.”. Treating both operands as the string types, it appends the right-hand operand to the left-hand operand, the result is ofcourse, a string.

$first_name = “John”;
$last_name = “Davis”;
print $first_name . $last_name; //outputs “John Davis”

Arithmetic Operators

Arithmetic operators are also used in many programming languages. You know for sure what each of them do, so we’ll just stick to point them out: addition “+”, subtraction “-”, division “/”, multiplication “*”, and modulus “%”.

<?php

/* define some variables */
$mean = 5;
$median
$mode = 9;

//post-increment operator
$mean++;
//$mean now equals 6

//pre-increment operator
++meanx;
//$mean is now 7

//post-decrement operator
$mean--;
//$mean is down to 6

//pre-decrement operator
--$mean;
//$mean is down to 5

//addition operator
$median = $mean + $mode;
//$median now equals 14

//substraction operator
$median = $mode - $mean;
//$median now equals 4

php?>

Comparison Operators

You've already seen some of the arithmetic and string operators in PHP's. However, the language also comes with operators that are designed specifically to compare two values: These operators are called "comparison operators". Here's an example to demonstrates Comparison Operators in action:

<?php

/* define some variables */
$mean = 9;
$median = 10;
$mode = 9;

// less-than operator
// returns true if left side is less than right
// returns true here
$result = ($mean < $median);
print "result is $result<br /> ";

// greater-than operator
// returns true if left side is greater than right
// returns false here
$result = ($mean > $median);
print "result is $result<br /> ";

// less-than-or-equal-to operator
// returns true if left side is less than or equal to right
// returns false here
$result = ($median <= $mode);
print "result is $result<br /> ";

// greater-than-or-equal-to operator
// returns true if left side is greater than or equal to right
// returns true here
$result = ($median > = $mode);
print "result is $result<br /> ";

// equality operator
// returns true if left side is equal to right
// returns true here
$result = ($mean == $mode);
print "result is $result<br /> ";

// not-equal-to operator
// returns true if left side is not equal to right
// returns false here
$result = ($mean != $mode);
print "result is $result<br /> ";

// inequality operator
// returns true if left side is not equal to right
// returns false here
$result = ($mean <> $mode);
print "result is $result";

php?>

PHP Functions

Function play a very important role in any programming language, including PHP.They are pieces of code which takes in some value processes it and produce results.

Function with no Arguments:

For a funtion to process on require some arguments to be passed to it. This is not the case always, some funtions require no arguments. such funtion outputs the same message whenever it is called on. This is illustrated in the example below.

function display_goodbye_message() //no semicolon here!
{
print “<h1>Thanks for visiting our web-site</h1>”;
}

Whenever this function is called on, it outputs the same message. It takes no arguments and doesn't return anything.

Function to Perform Calculation

The "return" statement is used to send the result to the function. Here in this case the result is calculated value of the purchase (which is number of items purchased multiplied by price)

function calculate_value($price, $items)
{
return ($price * $items); //returns a result
}

Calling a Function Dynamically

A function can be called dynamically in the same way we access dynamic variables. We can treat an expression's name as a funtion name and thus can call it.

$function_name = “calculate_value”;
$function_name(40, 5);

This is identical to:
calculate_value(40, 5);

Global statement in a Function.

When we want to access some important information which are outside the function, and without using arguments. Then we have to use the "global" statement.

Here we have used the global statement to tell the function that "$exchange_rate" is declared outside the the function. If we wont declare like this then the function would have returned zero, since $exchange_ratewould have been "NULL".

PHP Forms

Setting up a form in PHP script is exactly the same as in HTML

Setting Up Your Form

As in HTML, the form elements are enclosed within <form> tags. Here is a small example.

<form action="process.php" method="post">
Form elements and formatting etc.
</form<

The form element takes two values, First is the form's "action" that tells to which script the data has to be sent. In the example above it is "process.php". It can also be in the form of URL (e.g. http://www.vyom.co.in/scripts/private/processors/process.php) Second is the "method" which tells the form how to send the data. POST method sends data in data stream, and maintains it as a secret. like password GET method is used to send data making visible to users. For example if we are sending a name=george then it would look like (e.g. http://www.vyom.co.in/process.php?name=george)

Getting The Form Information

The variable that the form passes on by POST method is collected using $_POST. In the following example it takes variable from the POST and assigns it to the variable $name

$name=$_POST['variable'];

If we are using GET method to pass the data then should use the following code.

$variablename=$_GET['variable'];

For each variable that is passed from form, we should follow the above procedure.

How to create form to mail script

The following code is to create a system which will e-mail a user's comments to you.

HTML
<form action="mail.php" method="post"> Your Name: <input type="text" name="name"><br> E-mail: <input type="text" name = "email"><br><br> Comments<br> <textarea name="comments"></textarea><br><br> <input type="submit" value="Submit"> </form>

The above code is used to make a simple form, where a user can enter their e-mail address. name and comments if any. Here can add extra parts if required. After adding remember to update the php script too.

PHP

<?
function checkOK($field)
{
if (eregi("\r",$field) || eregi("\n",$field)){
die("Invalid Input!");
}
}
$name=$_POST['name'];
checkOK($name);
$email=$_POST['email'];
checkOK($email);
$comments=$_POST['comments'];
checkOK($comments);
$to="php@vyom.co.in";
$message="$name just filled in your comments form. They said:\n$comments\n\nTheir e-mail address was: $email";
if(mail($to,"Comments From Your Site",$message,"From: $email\n")) {
echo "Thanks for your comments.";
} else {
echo "There was a problem sending the mail. Please check that you filled in the form
correctly.";
}
?>

here we have used php@vyom.co.in, You should replace it with your own e-mail address. save the script as mail.php and upload both the files. And now just fill in your comment box.

First part of the script stops the spammers from using your form to send their spam messages. this is done by checking for special characters not present in the input that can be used to trick the computer into sending messages to other addresses. It is this function which checks for these characters. and if they are found, stops running the script.

PHP Includes

The include() function includes and evaluates the specified file. The include() statement takes all the contents of the specified file andcopies it to the one which consist this statement.

include()

The include() function includes and evaluates the specified file.
A D V E R T I S E M E N T

The include() statement takes all the contents of the specified file and copies it to the one which consist this statement.

vars.php
<?php
$color = 'green';
$fruit = 'apple';
?>

test.php
<?php
echo "A $color $fruit"; // A
include 'vars.php';
echo "A $color $fruit"; // A green apple
?>

require().

Similarly the require() statement includes and evaluates the specified file. Both include() and require() works in same way, the only difference is how they handle failure. The include() statement produces warning, but the script will continue its execution. While the require() statement produces a Fatal Error and script stop its execution.

Warning:
require(wrongFile.php) [function.require]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5

Fatal error:
require() [function.require]:
Failed opening required 'wrongFile.php'
(include_path='.;C:\php5\pear')
in C:\home\website\test.php on line 5

PHP Files

There are many built-in functions in PHP to handle files and directories. Using these functions we can read, write, delete, and get lots of information of the files
There are many built-in functions in PHP to handle files and directories. Using these functions we can read, write, delete, and get lots of information of the files.

To perform any funtion on a file we should have the right permission which will allow us to manupulate that file.

Creating and Deleting a File

We can create a file using the funtion "touch()". The touch() funtion when called first searches whether the specified file exists or not if the file doesnot exists it creates one with the specfied file name. To delete a file we use the function called "unlink()". This funtion removes the file that has been sent as an argument.

touch(“newinfo.txt”); //create a new file, if it doesn’t already exist

unlink(“oldinfo.txt”); //delete a file

Open Existing File

When a file got created, How to access it?
We can access an existing file using the funtion called "fopen()". This funtion takes two arguments, The first argument specifies the name of the file that has to be opened, and the second argument specifies in which mode the file has to be opened.i'e in "read-r", "write-w" or both "read-write" mode.

If the function fopen() executes successfully then it returns an integer value known as a file pointer. This value should be stored in a variable. This variable is used to work on with the opened file. If the funtion fopen() fails executing for any reason, It just returns FALSE. Once the file is used we should close it using the "fclose()" function. This function takes only the file name as the argument.

$oldfp = fopen(“oldinfo.txt”, “r”); //opens a file for reading

if(!$fp = fopen(“newinfo.txt”, “w”)) //tries to open a file for writing

die(“Error on opening file!”); //terminates the execution of the script if it cannot open the file

fclose($oldfp);

Reading from Files

To read from the file we use the funtion called "fgets()". When this funtion is called, it reads out all the characters until a newline(\n), or End Of File(EOF), or till a specified length is reached.

The function "fgets()" is similar to "fgets()", Unlike fgets() it returns a single character from a file. there is no need to specify any length as a argument, since a character is always 1 byte.

$text = fgets($fp, 2000); //reads 2000 bytes at most

$chr = fgetc($fp); //reads 1 byte only

More File Handling Functions

There are a lot of other functions that you can use with files like: testing functions – “file_exists()”, “is_file()”, “is_dir()”, “is_readable()”, “is_writeable()”, “is_executable()”; functions that return information on files: “filesize()”, “fileatime()”, “filemtime()”, “filectime()”. You can figure out what the function does by just reading its name.

Following table contains few File Handling functions and their description

Example	Description Preview
chdir	Changes PHP's current directory to specified directory. Returns TRUE on success or FALSE on failure.
chroot	Change the root directory
closedir	Closes a directory handle previously opened with opendir().
copy	Makes a copy of a file. Returns TRUE if the copy succeeded, FALSE otherwise.
dir	dir -- directory class class dir { dir(string directory); string path; resource handl...
file	Returns the contents of a file in an array.
filesize	Gets file size
fopen	Opens a file handle to be used .
fread	Reads the contents of a file descriptor assigned with fopen().
fwrite	Writes to a file descriptor opened with fopen().
getcwd	gets the current working directory string. getcwd (void) Returns the current working directory.
opendir	Returns a directory handle that can be used with readdir(), closedir() and rewinddir().
readdir	Reads the next file from a directory handle opened with opendir().
rename	Renames a file from the old file name to the new file name.
rewinddir	rewind directory handle, void rewinddir ( resource dir_handle) Resets the directory stream indicated by dir_handle to the beginning of the directory.
scandir	List files and directories inside the specified path
Unlink	Deletes a file.

PHP Cookies

After a request from script or a server user's browser stores small amount of data, This data is called cookie.

Cookie can be accessed in three ways by a PHP script:

In a cookie there are information about a name, value, expiry date, host and path. As cookies are sent from server through HTTP header, they end up to the user. Here are the 3 ways to access cookies:

using “$HTTP-COOKIE” which is the environmental variable, all cookie names and values are present in this variable.
using global variable “$cookie_name”, here the name should be replaced
using “HTTP_COOKIE_VARS [“cookie_name”]” which is a global array variable. (here replace the “cookie_name” by actual name of the cookie).

print $HTTP_COOKIE; //outputs “visits=23”
print getenv(“HTTP_COOKIER”); //outputs “visits=23”
print $visits; //outputs “23”
print $HTTP_COOKIE_VARS[visits]; //outputs “23”

How to Set a Cookie with PHP

“header()” function, or “setcookie()” function can be used to set cookie with PHP. The main purpose of “header()” function is not to set a cookie, and works just like “setcookie()”. Cookie header is written by ourself by using “header()” funtion, but “setcookie()” is much automated.

//don’t output anything before this...
header(“visits=23; expires=Friday, 15-Nov-06 03:27:21 GMT; path=/; domain=softwareprojects.org”);
setcookie(“hits”, 23, time() + 3600, “/”, “softwareprojects.org”, 0); //notice this last extra argument

Weather the cookies will be send over a secure connection or not is denoted by the last argument to "setcookie()" function. Here "0" means no and "1" means yes.

How to Retrieve a Cookie Value

To retrieve a cookie value, PHP $_COOKIE variable is used. In the following example the value of cookie named "user" is retrieved and displayed on the page.

<?php
// Print a cookie
echo $_COOKIE["user"];

// A way to view all cookies
print_r($_COOKIE);
?>

How to Delete a cookies

To delete a cookie we should SET the cookie we want to delete with the date that has already expired. While doing so we should include the same path, secure parameters and domain which was originally used to set the cookie.

setcookie(“visits”, 23, time() - 60, “/”,“vyom.co.in”, 0)

Weather the cookies will be send over a secure connection or not is denoted by the last argument to "setcookie()" function. Here "0" means no and "1" means yes.

Limitations of cookies

Apart from the advantage of passing information from one page to another page or visit to visit, Cookies do have some limitations. The maximum number of cookies that can be stored by the browser is 20.And maximum size of the cookie is 4KB. The user's privacy is maintained since only the originating host can read the data that has been stored.

PHP Session

A session-enabled page allocates unique identifiers to the users the first time they access the page, and then re-associates them with previously allocated ones when they return to the page
Besides cookies, there is one more way to pass information to different web-pages: Sessions.
A D V E R T I S E M E N T

A session-enabled page allocates unique identifiers to the users the first time they access the page, and then reassociates them with previously allocated ones when they return to the page. Any global variables which were associated with the session will then become available to your code.

The difference between sessions and cookies

The main difference between sessions and cookies is that a session can hold multiple variables, and you need not have to set cookies for every variable. By default, the session data is stored in the cookie wich has an expiry date of zero, which means that the session remains active only as long as the browser.Once you close the browser, all the stored information is lost. This behavior can be modified by changing the “session. cookie_lifetime” setting in “php.ini” from zero to whatever you want the cookie lifetime to be.

How to Start a Session

Before starting to work with sessions, you must explicitly start a session using “session_start()” function. If you want sessions to start themselfs automatically, you should enable the “session.auto_start” setting in PHP’s configuration file.

session_start();
//starts or resumes a function
print “Your session ID is: “ . session_id();
//displays the session ID
session_destroy();
//ends the session; comment this line and the browser will output the same session ID as before

After starting a session, you can access to the session ID via the “session_id()” function. After completing the work, you can destroy the session using “session_destroy()”.

Register Variables to a Session

the main objective of the session is to hold the values of variables. You must register session variables using the “session_register()” function, before trying to read them on a session-enabled page. Remember that a “session_register()” requires you to pass as an argument "variable name", and not the variable itself:

<?php
session_start();
?>
<html>
<body>
<?php
if(isset($stored_var))
{
print $stored_var; //this will not be displayed the first time you load the page, because you haven’t registered the variable yet!
}
else
{
$stored_var = “Hello from a stored variable!”;
session_register(“stored_var”); //don’t do this: session_register($session_var)
}
?>
</body>
</html>

you can test if a variable is assigned using the “isset()” function.

Remove the Registered Variables

To remove the registered variables, you need to use the session_unset() function. This function when called destroys all variables associated with a session, both in the the script and within session file .

<?php
session_start();
?>
<html>
<body>
<?php
session_register("test");
$test = 12;
print $test;//outputs 12 session_unset(); //$test is destroyed
session_destroy();
print $test; //outputs nothing
?>
</body>
</html>

PHP Email

The major advantage of server side scripting language is that, it provides a way to take a form input from a server and send e-mail to a particular e-mail address
The major advantage of server side scripting language is that, it provides a way to take a form input from a server and send e-mail to a perticular e-mail address.
A D V E R T I S E M E N T

The Mail Command

Many of the scripting languages require special set up(like CGI) to send an e-mail, But with PHP it is very easy, since it uses one simple command called mail(). This command is used as follows.

mail($to,$subject,$body,$headers);

The recepients address to whom mail has to be sent is mentioned using the $to variable. Subject line is mentioned using the $subject. And finally the body of the mail is denoted by $body variable.

If at all any additional headers has to be added to the mail then $headers is used. For example if we want to add cc(carbon copy) and bcc(blank carbon copy) headers then this variable can be used.

Sending An E-mail

Befopre sending the mail you should have to set the variable content that are to be used in mail command. Here is a simple code that illustrate this.

$to = "php@vyom.co.in";
$subject = "This is PHP Script";
$body = "PHP is one of the best scripting language";
$headers = "From: webmaster@gowansnet.com\n";
mail($to,$subject,$body,$headers);
echo "Mail sent to $to";

Here e-mail is from webmaster@vyom.co.in. This code performs two things.

Firstly it will send a message to php@vyom.co.in with
subject:'This is PHP Script'and
text: PHP is one of the best scripting language
Secondly It will output the
text:Mail sent to php@vyom.co.in to the browser.

Something you may have noticed from the example is that the From line ended with \n. This is acutally a very important character when sending e-mail. It is the new line character and tells PHP to take a new line in an e-mail. It is very important that this is put in after each header you add so that your e-mail will follow the international standards and will be delivered.

The \n code can also be used in the body section of the e-mail to put line breaks in but should not be used in the subject or the To field

Error Control

if(mail($to,$subject,$body,$headers))
{
echo "An e-mail was sent to $to with the subject: $subject";
}
else
{
echo "There was a problem sending the mail. Check your code and make sure that the e-mail address $to is valid";
}

In this code the mail() function is taken into a IF loop, If the the funtion executes properly, then the echo statement inside the IF funtion is executed saying that the mail has been sent. Otherwise it displays the error message saying that the mail has not sent and suggests to correct the problem.

PHP Sql

The process of accessing and working with a database connection from within a PHP script is as follows.

First you need to establish a connection to the database server.

You should have to validate any user input

Then select the database on the server to use.

Execute all the desired query against the database.

Furter retrieve and process the results.

Then create HTML or perform actions based on results.

Finally close the database connection.

How to connect to MySQL Database?

The first step here is to connect to the database, This is done via the mysql_connect() function, whose syntax is as follows:

mysql_connect($server , $username , $password )

<?php
$con = mysql_connect("localhost","henry","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}// some code
?>

The first parameter $server which we have passed, is the address of MySQL server to connect using the username and password provided by the $username and $password parameters.

How to close a Database Connection

Though not strictly necessary, sometimes it is advantageous to close an open connection to the database when it is no longer needed, Instead of waiting for an end of the request, while PHP will do so automatically. The syntax of mysql_close() function is as follows.

mysql_close($link)

where the parameter $link is the database connection resource returned from the mysql_connect() function.

How to select the Database to Use?

Once you have set up a database connection, the next step is to select the database on which you willbe performing queries(This is similar to SQL USE). To do so, you need the mysql_select_db() function which has the following syntax:

mysql_select_db($database , $link);

<?php
$con = mysql_connect("localhost","henry","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}// some code

mysql_select_db("my_db", $con);

mysql_close($con);
?>

Here $my_db is the name of database, and the other parameter $con which is optional is the database connection resource returned by the mysql_connect() function. This function attempts to select the specified database and return a Boolean value indicating the success or failure.

How to perform Query against a Database

To perform a query against the database within PHP, we make use of mysql_query() function, whose syntax is as follows:

mysql_query($query , $link);

<?php
$con = mysql_connect("localhost","henry","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}// some code

mysql_select_db("my_db", $con);
$result = mysql_query("SELECT * FROM person");
mysql_close($con);
?>

where $result holds the result of the query executed. Query is written inside the mysql_query function(without the terminating semi-colon or \g), the optional parameter $con is the value returned by the function mysql_connect(). And if the database is not closed, then PHP will use the last opened connection.

How to retrieving a Result Set?

PHP has many different methods to access the data from a result set, but they all have the same general form. Here we are showing the examle with the context of mysql_fetch_row() function. Its syntax is as follows:

mysql_query($query , $link);

<?php
$con = mysql_connect("localhost","henry","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}// some code

mysql_select_db("my_db", $con);
$result = mysql_query("SELECT * FROM person");
while($row = mysql_fetch_array($result))
{
echo $row['FirstName'] . " " . $row['LastName'];
echo "<br />";
}
mysql_close($con);
?>

where $result holds the result returned from a successful query executed using the function mysql_query(). This function returns a single row from the result set when called , in the form of enumerated array, where element "0" represents the first column, element "1" represents the second, and so on. Each subsequent call to the funtion will return the subsequent row in the result set until no row remains. Then the function mysql_fetch_row() returns a boolean false. Generally mysql_fetch_row() function is used in conjunction with the while loop to retrieve the entire array as shown in the above example.

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