Web II (PHP) (12)

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 Web II (PHP and MySQL Database Connectivity)

What is PHP?

The PHP Hypertext Preprocessor (PHP) is a programming language that allows web developers to create dynamic content that interacts with databases. PHP is basically used for developing web based software applications. It is a widely-used, free and opensource scripting language. The main feature of PHP from something like client-side JavaScript is that the code is executed on the server, generating HTML which is then sent to the client.

Basic Syntax of PHP

<html>

<head>

<title>Hello World</title>

</head>

<body>

<? php

echo "Hello, World!" ;

?>

</body>

</html>

Character functions in PHP

strlen( ): Counting the number of character inside the string.

strlen($my_str);

str_word_count( ): Counting the number of words in a string.

str_word_count(my_str);

str_replace( ): Replaces the searched text inside the string.

str_replace("facts", "truth", $my_str);

strrev( ): reverses the string.

strrev($my_str);

Get and Post Methods in PHP

There are two ways the browser client can send information to the web server.

GET Mehod

The GET method is used to submit the HTML form data. This data is collected by the predefined $_GET variable for processing. The information sent from an HTML form using the GET method is visible to everyone in the browser's address bar,

Advantages of GET method

 You can bookmark the page with the specific query string because the data sent by the GET method is displayed in URL.

 GET requests can be cached.

 GET requests are always remained in the browser history.

Disadvantages of GET Method

 The GET method should not be used while sending any sensitive information.

 A limited amount of data can be sent using method = "get". This limit should not exceed 2048 characters.

 For security reasons, never use the GET method to send highly sensitive information like username and password, because it shows them in the URL.

 The GET method cannot be used to send binary data (such as images or word documents) to the server.

POST Method

POST method is also used to submit the HTML form data. But the data submitted by this method is collected by the predefined superglobal variable $_POST instead of $_GET. GET method, it does not have a limit on the amount of information to be sent.

Advantages of POST method

 The POST method is useful for sending any sensitive information because the information sent using the POST method is not visible to anyone.

 There is no limitation on size of data to be sent using the POST Method. You can send a large amount of information using this method.

 Binary and ASCII data can also be sent using the POST method.

 Data security depends on the HTTP protocol because the information sent using the POST method goes through the HTTP header. By using secure HTTP, you can ensure that your data is safe.

Disadvantages of POST Method

 POST requests do not cache.

 POST requests never remain in the browser history.

 It is not possible to bookmark the page because the variables are not displayed in URL.

What is -> in PHP?

This is referred to as the object operator, or sometimes the single arrow operator. It is an access operator used for access/call methods and properties in a PHP object in Object-Oriented Programming (OOP)

 

 

Database Connectivity

Index.php

<html>

<body>

<form action = "insert.php" method = "post">

Username: <input type = "text" name = "username" /> <br>

Blood Group: <input type = "text" name= "bloodgroup" /><br>

<input type = "submit" />

<br>

</form>

<form action="display.php"method="post">

<br>

Serial No.: <input type="text" name="sno">

<br>

<input type="submit">

</form>

</body>

</html>

connect.php

<?php

$servername = "localhost";

$username = "root";

$password = "";

$dbname = "amc";

// Create connection

$conn = new mysqli($servername,$username,$password,$dbname);

// Check connection

if ($conn->connect_error) {

  die("Connection failed: " . $conn->connect_error);

}

else

{

echo "Connected successfully";

}

?>

insert.php

<?php

include("connect.php");

// Inserting data into table

$sname=$_REQUEST['username'];

$blood_group=$_REQUEST['bloodgroup'];

$sql = "INSERT INTO registration (name, blood_group)

VALUES ('$sname', '$blood_group')";

if ($conn->query($sql) === TRUE) {

  echo "<br>"."New record added successfully";

} else {

  echo "Error: " . $sql . "<br>" . $conn->error;

}

 $conn->close();

?>

 

display.php

<?php

include("connect.php");

//displaying data from table to html

  $sql = "SELECT sno, name, blood_group FROM registration";

  $result = $conn->query($sql);

  if ($result->num_rows > 0) {

// output data of each row

                echo "<br> Your searched result is <br>";

  while($row = $result->fetch_assoc()) {

                $sno=$_REQUEST['sno'];

                if($row["sno"]=="$sno")

                {

                echo"<table border=1>

                <tr>

                <th> S.No. </th>

                <th> Name </th>

                <th> Blood Group</th>

                </tr>

                <tr>

                <td>".$row["sno"]."</td>

                <td>".$row["name"]."</td>

                <td>".$row["blood_group"]."</td>

                </table>"

                ;

  }    }  } else {  echo "0 results";  }

?>

 

Learn to understand above code

mysqli( )

The MySQLi functions allows you to access MySQL database servers.

connect_error

Return the error description from the last connection error, if any

close( )

Close a previously opened database connection:

die( )

The die() is an inbuilt function in PHP. It is used to print message and exit from the current php script. It is equivalent to exit() function in PHP. Syntax :

die($message)

fetch_assoc( )

Fetch a result row as an associative array:

error( )

Return the last error description for the most recent function call, if any.

num_rows

Return the number of rows in a result set.

$_REQUEST

$_REQUEST is a PHP super global variable which is used to collect data after submitting an HTML form.

SQL statements

SQL SELECT Statement

SELECT sno, name, blood_group FROM registration;

SQL DISTINCT Clause : used to return only distinct (different) values.

SELECT DISTINCT sno, name, blood_group  FROM table_name;

SQL WHERE Clause

SELECT sno, name, blood_group  FROM registration WHERE blood_group='B +ve';

SQL AND/OR Clause

SELECT * FROM Customers WHERE Country='Germany' AND City='Berlin';

SELECT * FROM Customers WHERE Country='Germany' OR Country='Spain';

SQL IN Clause

SELECT * FROM Customers WHERE Country IN ('Germany', 'France', 'UK');

SQL BETWEEN Clause

SELECT * FROM Products WHERE Price BETWEEN 10 AND 20;

SQL LIKE Clause

Starting with 'a': SELECT * FROM Customers WHERE CustomerName LIKE 'a%';

Ending with 'a': LIKE '%a'

That have "or" in any position: LIKE '%or%';

That have "r" in the second position: LIKE '_r%';

Starts with "a" and are at least 3 characters in length: LIKE 'a__%';

Starts with "a" and ends with "o": LIKE 'a%o';

That does NOT start with "a": NOT LIKE 'a%';

SQL ORDER BY Clause

SELECT * FROM Customers ORDER BY Country;

SQL GROUP BY Clause

SELECT COUNT(CustomerID), Country FROM Customers GROUP BY Country;

SQL COUNT Clause

SELECT COUNT(ProductID) FROM Products;

SQL HAVING Clause

SELECT COUNT(CustomerID), Country FROM Customers GROUP BY Country

HAVING COUNT(CustomerID) > 5;

SQL CREATE TABLE Statement

CREATE TABLE Persons ( PersonID int, LastName varchar(255), FirstName varchar(255),
    Address varchar(255), City varchar(255));

SQL DROP TABLE Statement : deletes a table

DROP TABLE Shippers;

SQL CREATE INDEX Statement

CREATE INDEX idx_pname ON Persons (LastName, FirstName);

SQL DROP INDEX Statement

ALTER TABLE Person DROP INDEX idx_pname;

SQL DESC Statement: to sort the data returned in descending order.

SELECT * FROM Customers
ORDER BY CustomerName DESC;

SQL TRUNCATE TABLE Statement: deletes the data inside a table

TRUNCATE TABLE Categories;

SQL ALTER TABLE Statement

ALTER TABLE Customers ADD Email varchar(255);

ALTER TABLE Customers DROP COLUMN Email;

ALTER TABLE Customers MODIFY Email varchar(200);

SQL ALTER TABLE Statement (Rename)

ALTER TABLE employees RENAME COLUMN id TO employ_id;

ALTER TABLE Student RENAME TO Student_Details;

SQL INSERT INTO Statement

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway');

SQL UPDATE Statement

UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;

SQL DELETE Statement

DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';

SQL CREATE DATABASE Statement

CREATE DATABASE testDB;

SQL DROP DATABASE Statement

DROP DATABASE testDB;

SQL USE Statement

USE candy;

SQL COMMIT Statement

DELETE from Customer where State = 'Texas';

COMMIT;

SQL ROLLBACK Statement

DELETE FROM CUSTOMERS   WHERE AGE = 25;

ROLLBACK;

 

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