Learn PHP, PHP Advance MYSQL HTML, and Many Other Computer Programs: December 2009

Thursday, December 31, 2009

PHP Looping For Loops

Loops execute a block of code a specified number of times, or while a specified condition is true.

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The for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

for (init; condition; increment)
{
code to be executed;
}
Parameters:

• init: Mostly used to set a counter (but can be any code to be executed once at the beginning of the loop)

• condition: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.

• increment: Mostly used to increment a counter (but can be any code to be executed at the end of the loop)

Note: Each of the parameters above can be empty, or have multiple expressions (separated by commas).

Example

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>

<?php
for ($i=1; $i<=5; $i++)
{
echo "The number is " . $i . " ";
}
?>

</body>
</html>

Output:

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

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The foreach Loop

The foreach loop is used to loop through arrays.

Syntax
foreach ($array as $value)
{
code to be executed;
}

For every loop iteration, the value of the current array element is assigned to $value (and the array pointer is moved by one) - so on the next loop iteration, you'll be looking at the next array value.

Example

The following example demonstrates a loop that will print the values of the given array:

<html>
<body>

<?php
$x=array("one","two","three");
foreach ($x as $value)
{
echo $value . " ";
}
?>

</body>
</html>

Output:
one
two
three

PHP Looping While loops

Loops execute a block of code a specified number of times, or while a specified condition is true.

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PHP Loops

Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

In PHP, we have the following looping statements:
• While - loops through a block of code while a specified condition is true

• do...while - loops through a block of code once, and then repeats the loop as long as a specified condition is true

• for - loops through a block of code a specified number of times

• foreach - loops through a block of code for each element in an array

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The while Loop

The while loop executes a block of code while a condition is true.

Syntax
while (condition)
{
code to be executed;
}

Example

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:
<html>
<body>

<?php
$i=1;
while($i<=5)
{
echo "The number is " . $i . " ";
$i++;
}
?>

</body>
</html>

Output:

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

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The do...while Statement

The do...while statement will always execute the block of code once, it will then check the condition, and repeat the loop while the condition is true.
Syntax
do
{
code to be executed;
}
while (condition);

Example

The example below defines a loop that starts with i=1. It will then increment i with 1, and write some output. Then the condition is checked, and the loop will continue to run as long as i is less than, or equal to 5:

<html>
<body>

<?php
$i=1;
do
{
$i++;
echo "The number is " . $i . " ";
}
while ($i<=5);
?>

</body>
</html>

Output:

The number is 2
The number is 3
The number is 4
The number is 5
The number is 6

PHP Arrays

An array stores multiple values in one single variable.

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What is an Array?

A variable is a storage area holding a number or text. The problem is, a variable will hold only one value.
An array is a special variable, which can store multiple values in one single variable.
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
$cars1="Saab";
$cars2="Volvo";
$cars3="BMW";

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?
The best solution here is to use an array!
An array can hold all your variable values under a single name. And you can access the values by referring to the array name.
Each element in the array has its own index so that it can be easily accessed.
In PHP, there are three kind of arrays:

• Numeric array - An array with a numeric index

• Associative array - An array where each ID key is associated with a value

• Multidimensional array - An array containing one or more arrays
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Numeric Arrays

A numeric array stores each array element with a numeric index.
There are two methods to create a numeric array.

1. In the following example the index are automatically assigned (the index starts at 0):

$cars=array("Saab","Volvo","BMW","Toyota");
2. In the following example we assign the index manually:
$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";
Example

In the following example you access the variable values by referring to the array name and index:

<?php
$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";
echo $cars[0] . " and " . $cars[1] . " are Swedish cars.";
The code above will output:
Saab and Volvo are Swedish cars.
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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.

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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?

PHP Switch Statement

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

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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>

PHP If-Else

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

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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
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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.
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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! ";
echo "Have a nice weekend!";
echo "See you on Monday!";
}
?>
</body>
</html>
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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>

Wednesday, December 30, 2009

PHP String Variable

A string variable is used to store and manipulate text.
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String Variables in PHP

String variables are used for values that contains 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.
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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.

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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).

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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.

PHP Variables

A variable is used to store information.
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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;
?>
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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.
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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)

PHP Syntax

PHP code is executed on the server, and the plain HTML result is sent to the browser.

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Basic PHP Syntax

A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.
On servers with shorthand support enabled you can start a scripting block with
<? and end with ?>.
For maximum compatibility, we recommend that you use the standard form (<?php) rather than the shorthand form.

<?php

?>

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.
Below, we have an example of a simple PHP script which sends the text "Hello World" to the browser:

<html>

<body>
<?php
echo "Hello World";
?>
</body>
</html>
Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text "Hello World".

Note: The file must have a .php extension. If the file has a .html extension, the PHP code will not be executed.

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Comments in PHP

In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

<html>
<body>
<?php

//This is a comment

/*

This is
a comment
block

*/
?>
</body>
</html>

Monday, December 28, 2009

PHP Installation

What do you Need?

If you supports PHP you don't need to do any thing.
just create some .php file in your web directory, and the server will parse them for you. because it is free, most web hosts offer PHP support.

How ever, if your server does not support PHP, must install PHP.

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 MYSQL Database
Download MYSQL for free Here: http://www.mysql.com/downloads/index.html

Download Appache server
Download Appache server for free here: http://httpd.apche.org/download.cgi

PHP Introduction

PHP is a server-side scripting language.
what you should already know.
Before you conitnue you should have a basic understanding of the following.

HTML/XHTML
Javascript

I will post later on these subjects.

What is PHP?

PHP stands for Hypertext preprocessor.
PHP is a server-side scripting language, like ASP.
PHP script are executed on the server.
PHP supports many databases (MYSQL, Informix, oracle, sybase solid , PostgreSQL, Generic ODBC, etc.).
PHP is an Open source software.
PHP is free to download and use .

What is a PHP file?

PHP file can contain text, HTML tags and scripts.
PHP file are returned to the browser as plain HTML.
PHP file have a file extension of ".php" , ".php3" ,or ".PHTML".

What is MYSQL?

MYSQL is database server.
MYSQL is ideal for both small and large applications.
MYSQL supports standard SQL.
MYSQL complies on a number of platform.
MYSQL is free to Download and use PHP+MYSQL.
PHP combined with MYSQL are cross platform (you can develop in windows and serve on a Unix platform).

Why PHP?

PHP runs on different platforms (windows, linux, unix, etc).
PHP is compatible with almost all servers used today(apache, IIS etc)
PHP is free to download from the official PHP resourse: http://www.php.net/

PHP Home

PHP is a power full tool for dynamic and interactive web pages. PHP is widely used , free, and efficient alternative to competitors such as microsoft's ASP.

In our PHP tutorial you will learn about PHP, and how to execute scripts on your server.

Learn PHP, PHP Advance MYSQL HTML, and Many Other Computer Programs