THOUGHTS

**The youth needs to develop an attitude : I can do it! We can do it !! India will do it!!! ""மரங்களை நடுவோம் பசுமை இல்ல விளைவை தடுப்போம்"" !!! PLEASE DO IT**

Wednesday, August 10, 2011

PHP Tutorial Part 2



Assignment Operators
Operator
Example
Is The Same As
=
x=y
x=y
+=
x+=y
x=x+y
-=
x-=y
x=x-y
*=
x*=y
x=x*y
/=
x/=y
x=x/y
.=
x.=y
x=x.y
%=
x%=y
x=x%y
Comparison Operators
Operator
Description
Example
==
is equal to
5==8 returns false
!=
is not equal
5!=8 returns true
> 
is greater than
5>8 returns false
< 
is less than
5<8 returns true
>=
is greater than or equal to
5>=8 returns false
<=
is less than or equal to
5<=8 returns true
Logical Operators
Operator
Description
Example
&&
And
x=6
y=3
(x < 10 && y > 1) returns true
||
Or
x=6
y=3
(x==5 || y==5) returns false
!
Not
x=6
y=3
!(x==y) returns true

 





PHP If...Else Statements



The if, elseif and else statements in PHP 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.
  • if...else statement - use this statement if you want to execute a set of code when a condition is true and another if the condition is not true
  • elseif statement - is used with the if...else statement to execute a set of code if one of several condition are true

The If...Else Statement

If you want to execute some code if a condition is true and another code if a condition is false, use the if....else statement.

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 ElseIf Statement

If you want to execute some code if one of several conditions are true use the elseif statement

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>

 


PHP Switch Statement



The Switch statement in PHP is used to perform one of several different actions based on one of several different conditions.

The Switch Statement

If you want to select one of many blocks of code to be executed, use the Switch statement.
The switch statement is used to avoid long blocks of if..elseif..else code.

Syntax

switch (expression)
{
case label1:
  code to be executed if expression = label1;
  break;
case label2:
  code to be executed if expression = label2;
  break;
default:
  code to be executed
  if expression is different
  from both label1 and label2;

}

Example

This is how it works:
  • A single expression (most often a variable) is evaluated once
  • The value of the expression is compared with the values for each case in the structure
  • If there is a match, the code associated with that case is executed
  • After a code is executed, break is used to stop the code from running into the next case
  • The default statement is used if none of the cases are true
<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>

PHP Arrays



An array can store one or more values in a single variable name.

What is an array?

When working with PHP, sooner or later, you might want to create many similar variables.
Instead of having many similar variables, you can store the data as elements in an array.
Each element in the array has its own ID so that it can be easily accessed.
There are three different kind of arrays:
  • Numeric array - An array with a numeric ID key
  • Associative array - An array where each ID key is associated with a value
  • Multidimensional array - An array containing one or more arrays

Numeric Arrays

A numeric array stores each element with a numeric ID key.
There are different ways to create a numeric array.

Example 1

In this example the ID key is automatically assigned:
$names = array("Peter","Quagmire","Joe");

Example 2

In this example we assign the ID key manually:
$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";
The ID keys can be used in a script:
<?php
$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";
echo $names[1] . " and " . $names[2] . 
" are ". $names[0] . "'s neighbors";
?>
The code above will output:
Quagmire and Joe are Peter's neighbors


Associative Arrays

An associative array, each ID key is associated with a value.
When storing data about specific named values, a numerical array is not always the best way to do it.
With associative arrays we can use the values as keys and assign values to them.

Example 1

In this example we use an array to assign ages to the different persons:
$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);

Example 2

This example is the same as example 1, but shows a different way of creating the array:
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";
The ID keys can be used in a script:
<?php
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";
echo "Peter is " . $ages['Peter'] . " years old.";
?>
The code above will output:
Peter is 32 years old.


Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.

Example

In this example we create a multidimensional array, with automatically assigned ID keys:
$families = array
(
  "Griffin"=>array
  (
  "Peter",
  "Lois",
  "Megan"
  ),
  "Quagmire"=>array
  (
  "Glenn"
  ),
  "Brown"=>array
  (
  "Cleveland",
  "Loretta",
  "Junior"
  )
);
The array above would look like this if written to the output:
Array
(
[Griffin] => Array
  (
  [0] => Peter
  [1] => Lois
  [2] => Megan
  )
[Quagmire] => Array
  (
  [0] => Glenn
  )
[Brown] => Array
  (
  [0] => Cleveland
  [1] => Loretta
  [2] => Junior
  )
) 

Example 2

Lets try displaying a single value from the array above:
echo "Is " . $families['Griffin'][2] . 
" a part of the Griffin family?";
The code above will output:
Is Megan a part of the Griffin family?

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