Saturday, October 29, 2011

PHP Looping - While Loops

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

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

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:

Output:

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

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 " . $i . "<br />";
  }
while ($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

The for loop and the foreach loop will be explained in the next chapter.

http://www.w3schools.com/php/php_looping.asp

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Saturday, October 22, 2011

PHP Arrays

An array stores multiple values in one single variable.

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

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.

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?

Complete PHP Array Reference
For a complete reference of all array functions, go to our complete PHP Array Reference.
The reference contains a brief description, and examples of use, for each function!

http://www.w3schools.com/php/php_arrays.asp

»» READMORE...

PHP Switch Statement

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

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

http://www.w3schools.com/php/php_switch.asp

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Friday, October 21, 2011

PHP If...Else Statements

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:

Notice that there is no ..else.. in this syntax. The code is executed 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!":

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!":

http://www.w3schools.com/php/php_if_else.asp

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Monday, October 17, 2011

PHP Operators

This section lists the different operators used in PHP.

Arithmetic Operators

Operator	Description	Example	Result
+	Addition	x=2 x+2	4
-	Subtraction	x=2 5-x	3
*	Multiplication	x=4 x*5	20
/	Division	15/5 5/2	3 2.5
%	Modulus (division remainder)	5%2 10%8 10%2	1 2 0
++	Increment	x=5 x++	x=6
--	Decrement	x=5 x--	x=4

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 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

http://www.w3schools.com/php/php_operators.asp

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Friday, October 14, 2011

PHP String Variables

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 string

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:

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 a character/text within a string.
If a match is found, this function will return the character 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 the example above is 6. The reason that it is 6 (and not 7), is that the first character position in the string is 0, and not 1.

Complete PHP String Reference

For a complete reference of all string functions, go to our complete PHP String Reference.
The reference contains a brief description, and examples of use, for each function!

PHP String Functions

PHP String Introduction

The string functions allow you to manipulate strings.

Installation

The string functions are part of the PHP core. There is no installation needed to use these functions.

PHP String Functions

PHP: indicates the earliest version of PHP that supports the function.

Function	Description	PHP
addcslashes()	Returns a string with backslashes in front of the specified characters	4
addslashes()	Returns a string with backslashes in front of predefined characters	3
bin2hex()	Converts a string of ASCII characters to hexadecimal values	3
chop()	Alias of rtrim()	3
chr()	Returns a character from a specified ASCII value	3
chunk_split()	Splits a string into a series of smaller parts	3
convert_cyr_string()	Converts a string from one Cyrillic character-set to another	3
convert_uudecode()	Decodes a uuencoded string	5
convert_uuencode()	Encodes a string using the uuencode algorithm	5
count_chars()	Returns how many times an ASCII character occurs within a string and returns the information	4
crc32()	Calculates a 32-bit CRC for a string	4
crypt()	One-way string encryption (hashing)	3
echo()	Outputs strings	3
explode()	Breaks a string into an array	3
fprintf()	Writes a formatted string to a specified output stream	5
get_html_translation_table()	Returns the translation table used by htmlspecialchars() and htmlentities()	4
hebrev()	Converts Hebrew text to visual text	3
hebrevc()	Converts Hebrew text to visual text and new lines (\n) into <br />	3
html_entity_decode()	Converts HTML entities to characters	4
htmlentities()	Converts characters to HTML entities	3
htmlspecialchars_decode()	Converts some predefined HTML entities to characters	5
htmlspecialchars()	Converts some predefined characters to HTML entities	3
implode()	Returns a string from the elements of an array	3
join()	Alias of implode()	3
levenshtein()	Returns the Levenshtein distance between two strings	3
localeconv()	Returns locale numeric and monetary formatting information	4
ltrim()	Strips whitespace from the left side of a string	3
md5()	Calculates the MD5 hash of a string	3
md5_file()	Calculates the MD5 hash of a file	4
metaphone()	Calculates the metaphone key of a string	4
money_format()	Returns a string formatted as a currency string	4
nl_langinfo()	Returns specific local information	4
nl2br()	Inserts HTML line breaks in front of each newline in a string	3
number_format()	Formats a number with grouped thousands	3
ord()	Returns the ASCII value of the first character of a string	3
parse_str()	Parses a query string into variables	3
print()	Outputs a string	3
printf()	Outputs a formatted string	3
quoted_printable_decode()	Decodes a quoted-printable string	3
quotemeta()	Quotes meta characters	3
rtrim()	Strips whitespace from the right side of a string	3
setlocale()	Sets locale information	3
sha1()	Calculates the SHA-1 hash of a string	4
sha1_file()	Calculates the SHA-1 hash of a file	4
similar_text()	Calculates the similarity between two strings	3
soundex()	Calculates the soundex key of a string	3
sprintf()	Writes a formatted string to a variable	3
sscanf()	Parses input from a string according to a format	4
str_ireplace()	Replaces some characters in a string (case-insensitive)	5
str_pad()	Pads a string to a new length	4
str_repeat()	Repeats a string a specified number of times	4
str_replace()	Replaces some characters in a string (case-sensitive)	3
str_rot13()	Performs the ROT13 encoding on a string	4
str_shuffle()	Randomly shuffles all characters in a string	4
str_split()	Splits a string into an array	5
str_word_count()	Count the number of words in a string	4
strcasecmp()	Compares two strings (case-insensitive)	3
strchr()	Finds the first occurrence of a string inside another string (alias of strstr())	3
strcmp()	Compares two strings (case-sensitive)	3
strcoll()	Locale based string comparison	4
strcspn()	Returns the number of characters found in a string before any part of some specified characters are found	3
strip_tags()	Strips HTML and PHP tags from a string	3
stripcslashes()	Unquotes a string quoted with addcslashes()	4
stripslashes()	Unquotes a string quoted with addslashes()	3
stripos()	Returns the position of the first occurrence of a string inside another string (case-insensitive)	5
stristr()	Finds the first occurrence of a string inside another string (case-insensitive)	3
strlen()	Returns the length of a string	3
strnatcasecmp()	Compares two strings using a "natural order" algorithm (case-insensitive)	4
strnatcmp()	Compares two strings using a "natural order" algorithm (case-sensitive)	4
strncasecmp()	String comparison of the first n characters (case-insensitive)	4
strncmp()	String comparison of the first n characters (case-sensitive)	4
strpbrk()	Searches a string for any of a set of characters	5
strpos()	Returns the position of the first occurrence of a string inside another string (case-sensitive)	3
strrchr()	Finds the last occurrence of a string inside another string	3
strrev()	Reverses a string	3
strripos()	Finds the position of the last occurrence of a string inside another string (case-insensitive)	5
strrpos()	Finds the position of the last occurrence of a string inside another string (case-sensitive)	3
strspn()	Returns the number of characters found in a string that contains only characters from a specified charlist	3
strstr()	Finds the first occurrence of a string inside another string (case-sensitive)	3
strtok()	Splits a string into smaller strings	3
strtolower()	Converts a string to lowercase letters	3
strtoupper()	Converts a string to uppercase letters	3
strtr()	Translates certain characters in a string	3
substr()	Returns a part of a string	3
substr_compare()	Compares two strings from a specified start position (binary safe and optionally case-sensitive)	5
substr_count()	Counts the number of times a substring occurs in a string	4
substr_replace()	Replaces a part of a string with another string	4
trim()	Strips whitespace from both sides of a string	3
ucfirst()	Converts the first character of a string to uppercase	3
ucwords()	Converts the first character of each word in a string to uppercase	3
vfprintf()	Writes a formatted string to a specified output stream	5
vprintf()	Outputs a formatted string	4
vsprintf()	Writes a formatted string to a variable	4
wordwrap()	Wraps a string to a given number of characters	4

PHP String Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant	Description	PHP
CRYPT_SALT_LENGTH	Contains the length of the default encryption method for the system. For standard DES encryption, the length is 2
CRYPT_STD_DES	Set to 1 if the standard DES-based encryption with a 2 character salt is supported, 0 otherwise
CRYPT_EXT_DES	Set to 1 if the extended DES-based encryption with a 9 character salt is supported, 0 otherwise
CRYPT_MD5	Set to 1 if the MD5 encryption with a 12 character salt starting with $1$ is supported, 0 otherwise
CRYPT_BLOWFISH	Set to 1 if the Blowfish encryption with a 16 character salt starting with $2$ or $2a$ is supported, 0 otherwise0
HTML_SPECIALCHARS
HTML_ENTITIES
ENT_COMPAT
ENT_QUOTES
ENT_NOQUOTES
CHAR_MAX
LC_CTYPE
LC_NUMERIC
LC_TIME
LC_COLLATE
LC_MONETARY
LC_ALL
LC_MESSAGES
STR_PAD_LEFT
STR_PAD_RIGHT
STR_PAD_BOTH

http://www.w3schools.com/php/php_string.asp

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Thursday, October 13, 2011

PHP Variables

Variables in PHP

Variables are used for storing 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)

http://www.w3schools.com/php/php_variables.asp

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PHP Syntax

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:

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.

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> http://www.w3schools.com/php/php_syntax.asp

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Tuesday, October 11, 2011

PHP Installation

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.
However, if your server does not support PHP, you 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 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/

Download Apache Server

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

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http://www.w3schools.com/php/php_install.asp

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Monday, October 10, 2011

PHP Introduction

PHP is a server-side scripting language.

What You Should Already Know

Before you continue you should have a basic understanding of the following:

HTML/XHTML
JavaScript

What is PHP?

PHP stands for PHP: Hypertext Preprocessor
PHP is a server-side scripting language, like ASP
PHP scripts 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 files can contain text, HTML tags and scripts
PHP files are returned to the browser as plain HTML
PHP files have a file extension of ".php", ".php3", or ".phtml"

What is MySQL?

MySQL is a database server
MySQL is ideal for both small and large applications
MySQL supports standard SQL
MySQL compiles on a number of platforms
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 resource: www.php.net
PHP is easy to learn and runs efficiently on the server side

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

http://www.w3schools.com/php/php_intro.asp

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