Monday, 2 March 2015

PHP AND MYSQL



PHP AND MYSQL

PHP- is the Hypertext preprocessor is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.
PHP is a server-side scripting language designed for web development but also used as a general-purpose programming language
PHP code can be simply mixed with HTML code, or it can be used in combination with various templating engines and web frameworks
Example of the PHP code in a HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>
        <title>Example</title>
    </head>
    <body>

        <?php
            echo "Hi, I'm a PHP script!";
        ?>

    </body>
</html>
 
PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)  PHP is free to download and use to develop web

PHP File- is the file that contains text, HTML tags and script this files are returned to the browser as a plan HTML.

PHP file have the file extension of “.php”, “.php3”, or “.phtml”

PHP runs on different platforms (Windows, Linux, Unix, etc.)
PHP is compatible with almost all servers used today (Apache, IIS, etc.)

 

MySQL

MySQL is a relational database management system (RDBMS) based on SQL (Structured Query Language).

MySQL is most often associated with web-based applications and online publishing and is an important component of an open source enterprise stack called LAMP.

MySQL runs on virtually all platforms, including Linux, UNIX, and Windows. Although it can be used in a wide range of applications

 

PHP + MySQL

PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)
With PHP, you can connect to and manipulate databases.
MySQL is the most popular database system used with PHP

 

Where to Start?

To get access to a web server with PHP support, you can:
  • Install Apache (or IIS) on your own server, install PHP, and MySQL
  • Or find a web hosting plan with PHP and MySQL support

What do you need?

If your server supports PHP you don't need to do anything.
Just create some .php files in your web directory, and the server will parse them for you. Because it is free, most web hosts offer PHP support.

Variables in PHP

Variables are used for storing a values, like text strings, numbers or arrays.
When a variable is declared, it can be used over and over again in your script.
All variables in PHP start with a $ sign symbol.
The correct way of declaring a variable in PHP:
$var_name = value;
 New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.
Let's try creating a variable containing a string, and a variable containing a number:
<?php
$txt="Hello World!";
$x=16;
?>

PHP is a Loosely Typed Language

In PHP, a variable does not need to be declared before adding a value to it.
In the example above, you see that you do not have to tell PHP which data type the variable is.
PHP automatically converts the variable to the correct data type, depending on its value.
In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.
In PHP, the variable is declared automatically when you use it.

Naming Rules for Variables

  • A variable name must start with a letter or an underscore "_"
  • A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
  • A variable name should not contain spaces. If a variable name is more than one word, it should be separated with an underscore ($my_string), or with capitalization ($myString)
A string variable is used to store and manipulate text.

String Variables in PHP

String variables are used for values that contain characters.
In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP.
After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the text "Hello World" to a string variable called $txt:<?php
$txt="Hello World";
echo $txt;
?>
The output of the code above will be:
Hello World
Now, lets try to use some different functions and operators to manipulate the string.

The Concatenation Operator

There is only one string operator in PHP.
The concatenation operator (.)  Is used to put two string values together.
To concatenate two string variables together, use the concatenation operator:
<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>
The output of the code above will be:
Hello World! What a nice day!
If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two strings.

The strlen() function

The strlen() function is used to return the length of a string.
Let's find the length of a string:
<?php
echo strlen("Hello world!");
?>
The output of the code above will be:  12
The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string).

The strpos() function

The strpos() function is used to search for character within a string.
If a match is found, this function will return the position of the first match. If no match is found, it will return FALSE.
Let's see if we can find the string "world" in our string:
<?php
echo strpos("Hello world!","world");
?>
The output of the code above will be:
6
The position of the string "world" in our string is position 6. The reason that it is 6 (and not 7), is that the first position in the string is 0, and not 1.

Conditional statements are used to perform different actions based on different conditions.

Conditional Statements
Very often when you write code, you want to perform different actions for different decisions.
You can use conditional statements in your code to do this.
In PHP we have the following conditional statements:
  • if statement - use this statement to execute some code only if a specified condition is true
  • if...else statement - use this statement to execute some code if a condition is true and another code if the condition is false
  • if...elseif....else statement - use this statement to select one of several blocks of code to be executed
  • switch statement - use this statement to select one of many blocks of code to be executed

The if Statement

Use the if statement to execute some code only if a specified condition is true.

Syntax

if (condition) code to be executed if condition is true;
The following example will output "Have a nice weekend!" if the current day is Friday:
<html>
<body>

<?php
$d=date("D");
if ($d=="Fri") echo "Have a nice weekend!";
?>

</body>
</html>
Notice that there is no ..else.. in this syntax. You tell the browser to execute some code only if the specified condition is true.

The if...else Statement

Use the if....else statement to execute some code if a condition is true and another code if a condition is false.

Syntax

if (condition)
  code to be executed if condition is true;
else
  code to be executed if condition is false;

Example

The following example will output "Have a nice weekend!" if the current day is Friday, otherwise it will output "Have a nice day!":
<html>
<body>

<?php
$d=date("D");
if ($d=="Fri")
  echo "Have a nice weekend!";
else
  echo "Have a nice day!";
?>

</body>
</html>
If more than one line should be executed if a condition is true/false, the lines should be enclosed within curly braces:
<html>
<body>

<?php
$d=date("D");
if ($d=="Fri")
  {
  echo "Hello!<br />";
  echo "Have a nice weekend!";
  echo "See you on Monday!";
  }
?>

</body>
</html>

The if...elseif....else Statement

Use the if....elseif...else statement to select one of several blocks of code to be executed.

Syntax

if (condition)
  code to be executed if condition is true;
elseif (condition)
  code to be executed if condition is true;
else
  code to be executed if condition is false;

Example

The following example will output "Have a nice weekend!" if the current day is Friday, and "Have a nice Sunday!" if the current day is Sunday. Otherwise it will output "Have a nice day!":
<html>
<body>

<?php
$d=date("D");
if ($d=="Fri")
  echo "Have a nice weekend!";
elseif ($d=="Sun")
  echo "Have a nice Sunday!";
else
  echo "Have a nice day!";
?>

</body>
</html>

The PHP Switch Statement

Use the switch statement to select one of many blocks of code to be executed.

Syntax         

switch (n)
{
case label1:
  code to be executed if n=label1;
  break;
case label2:
  code to be executed if n=label2;
  break;
default:
  code to be executed if n is different from both label1 and label2;
}
This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if no match is found.

Example

<html>
<body>

<?php
switch ($x)
{
case 1:
  echo "Number 1";
  break;
case 2:
  echo "Number 2";
  break;
case 3:
  echo "Number 3";
  break;
default:
  echo "No number between 1 and 3";
}
?>

</body>
</html>
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