Question and Answer

 Difference between Temp tables and Tables variables?
A. Temp Table in SQL Server: 
a. Temp table is the special type of tables which are used to store the intermediate data of the actual table.
b. Temp tables are only visible to the current sessions of the sql server instance. When the session end, these table data automatically drops.
c. We can’t join the temp tables as they don’t allow the foreign key constraints.
d. Temp tables are created in TempDB database.
e. We can use the same temp table name for the different user sessions.
f. Mostly used in stored procedure to handle the intermediate data.
41. What does @ and @@ suffixed by property names specify?
A. @- This is used for the variable declaration
e.g. @name varchar2(50)
@@- This is used for the Global variable declaration
e.g. @@Error=0
42. Self-join queries.
A. Self-Join is a type of join which is used to join the same table by creating the second instance of the same table. So we join 2 instances of the same table in case of self-join. This type of join is used when there is the requirement to get the referenced data which is available in the same table.
e.g. A table contains EmpId, Ename and ManagerId
As the manager id is also an employee id. Now if we want that who is the manager of which employee. In this situation, we need to create the instance of the same table and get the required data as:
SELECT EMPID, ENAME, ENAME AS [MANAGER NAME]
FROM EMP E1, EMP E2
WHERE E1.EMPID= E2.MANAGERID
43. Types of Index.
A.  Indexes are one the database objects which is used to improve the performance of the database queries. it reduces the table scan while retrieving the data from the database and the search gets fast-
There are 2 types of indexes used in the SQL server:
a. Clustered index
b. Non clustered index
There are 3 more types of index but those comes under the above two-
a. unique index
b. Composite Index
c. XML Index-added in SQL Server 2005
The index basically works on searching like binary tree where the root value is the finding value and it will be compared with the partitioned value of the tree.
44. Difference between Primary key, Unique key and Candidate key?
A. Primary Key- It is a key to make the unique identification of the row in a table. It doesn’t allow null values in the primary key column. We can create the lookup columns based on the primary key. One table allows maximum of 1 primary key and in 1 table, we can create the primary key column by using 16 columns. Due to one of the normalization rule, we have to create primary key for the table to make the rows unique.
Unique Key:- Primary Key+ Not null is called as unique key. Unique key is also used to make the rows as unique in a table. The only difference between primary key and unique key is that primary key doesn’t allow null value while the unique key allow. The limitation of the null in unique key is that it allows only one Null so in only one row; we can make the key as null for the unique key.
Candidate key- the key other than primary key to make the rows as unique is called as candidate key. In candidate key, we take the columns which are not in the primary key and make the key for uniqueness of the row.
45. What is the default value for Date type. What are Min and Max values for Date in 2008.
A.  The default value of Date is CURRENT_TIMESTAMP
Below are the new date and time values in Sql Server 2008:
In SQL Server 2008:
1. DateTime2
Min Value: 0001-01-01 00:00:00.0000000
Max Value: 9999-12-31 23:59:59.9999999
2. Date
Min Value: 0001-01-01
Max Value: 9999-12-31

WCF
46. What is WCF also known as?
A.  WCF (Windows Communication Foundation) is also know an  Indigo by its code name.
47. Difference between WCF and Web Services?
A. Below are the main differences between the WCF and Web Service:
Web Service:
a.    Can be hosted in IIS only
b.    Only two types of operations affects- One-Way, Request-Response
c.     To serialize the data use System.Xml.Serialization
d.    To encode the data use- XML 1.0, MTOM, DIME, Custom
WCF service:
a.    Can be hosted in IIS, Self Hosting, WAS, Windows Services etc
b.    Three types of operations affects- One-Way, Request-Response and Duplex
c.     To serialize the data use System.Runtimel.Serialization
d.    To encode the data use- XML 1.0, MTOM,Binary, Custom
e.    WCF Service can be accessed through HTTP, TCP, Named pipes, MSMQ,P2P etc.
48. What are Endpoints?
A. The collection of Address, Binding and Contract is called as End Point. In Sort,
EndPoint = A+B+C
Address (Where)-  it means where the service is hosted. URL of the service shows the address.
Binding (How)- How to connect to the service, is defined by the Binding. It basically has the definition of the communication channel to communicate to the WCF service
Contract (what)- It means what the service contains for the client. What all the methods are implemented in the WCF service is implemented in the Contract.
49. What are Behavior and Bindings?
A. Binding mainly describes about the communication of the client and service. For this, there are protocols corresponding to the binding behavior which will take care of the communication channel. There are different protocols which we use for the different types of bindings. E.g. HTTP, TCP, MSMQ, Named Pipes etc.
Behavior is used for the common configurations that could be for endpoints. When we use the common behavior, they affect to all the end points. Adding the service behavior affect the service related stuff while the endpoint related behavior affects the end points. Also operations level behavior affects the operations. 
50. What are different types of Contracts supported?
A. There are mainly 5 type of contracts used in WCF service:
a. Service Contract
b. Operation Contract
c. Data Contract
d. Message Contract
e. Fault Contract
51. What is the difference between Transport and Message Security mode?
A. WCF supports 2 types of security- Transport Level Security and Message Level Security
Transport Level Security- In this type of security, we make the transport channel as secure so that the data flows in that channel will be automatically secured. For HTTP channel, we use the client certificate for the security of the web address. SSL is used for the HTTP channel security. As we don’t need to secure each of the messages which are floating between the client and the service, the speed is faster as direct message is going to the client from the service.
Message level security- This type of security in WCF is used where we don’t have the fixed transport medium and we need to secure each message which is floating between the server and the client. In this type of security we use certain algorithms for making the message as secure message. We use some extra bits and send with the message. We also use some encryption techniques like SHA1 or MD5 which make the proper security for our message. As each message needs to be secured, this type of security makes some delay in the process of sending and receiving the messages.
52. How to configure WCF security to support Windows authentication?
A. To support the WCF security in Windows Authentication, we need to add the ClientCredetialType attribute to “Windows” under the security tab element:
transport clientCredentialType="Windows"
53. How to use Fault Contract?
A.  Fault Contract is mainly used for viewing and displaying the errors which occurred in the service. So it basically documents the error and the error message can be shown to the user in the understandable way. We can’t use here the try….catch block for the error handling because the try…catch is the technology specific (.Net Technology). So we use the Fault contract for the error handling.
e.g. To use the Fault contract, we can simply write like the below:
public  int Add(int number1,int number2)
{
  // write some implementation
 throw new FaultException (“Error while adding data..”);
}
Here the fault Exception method is the inbuilt method which will throw the exception and display the message . We can use the custom class so that the message can be customized and the customized message can be sent to the client.
So we can creeat  a clss like:
Public Class CustomException()
{
public int ID{get;set;}
public string Message{get;set;}
public string Type{get;set;}
}
Now this custom type we ca use with the Operation Contract as:
[ServiceContract] 
Public interface IMyInterface
{
[OperationContract]
[FaultContract(typeOf(CustomException))]
Int Add(int num1,int num2);
}
Now while implementation of the Add method, we can assign the class properties.
WPF
54. Diff between XML and XAML.
A. XAML is the declarative XML based language which is used to define the objects and properties. XAML document is loaded by XAML parser. So XAML Parser initiates the objects and set those properties. XAML is mainly used in creating the objects in WPF and Silverlight applications. 

55. Stack Panel and Wrap Panel.
A. StackPanel is one of layout control in WPF. We can place the child controls inside the stack panel either horizontally or vertically. So it provides two types of orientations- Horizontal Orientation and Vertical orientation.

Wrap panel is another layout control which is similar to the StackPanel . Wrap panel not only keep the control in horizontal and vertical orientation but also wrap them in to new line if there is no space. Here also the orientation can be set as Horizontal or Vertical. Its main use is to arrange the tabs in the tab control, menu control or in toolbar items.

56. Hierarchical Data Template.
A. Hierarchical Data Template is a type of data template which is used to bind the controls which  supports headeredItemsControl, like TreeviewItem or MenuItem.
We can bind those controls items using the Hierarchical Data Template. It displayed the data in to Hierarchical structure in the tree structure. It could be in the left to right or top to bottom.

57. Virtualization.
A. This is the feature in WPF which increases the efficiency of the programs when there are the large data objects. If the WPF ItemsControl is bound with the large collection data source object and we enabled the virtualization, then the controls will show only the data which is in the visual container for those items which are visible currently. This visual data is only the small part of the large data object. Now when the user will scroll down or up, the rest of the data will be visible and previous data will be hidden again. So this is increase the efficiency of the program from the UI prospective. 
58. Events and Routed Events.
A.  Routed event is special type of event which can invoke and handle multiple events from different objects rather than the event which is coming from one object. So it generally handles the object from the element tree. So whatever the elements inside the element tree and if they generate the event-may be multiple events, the routed event is capable of handling those events.
The routed event can be invoked in both the directions but in general it comes from the source element and then bubbled up in the element tree until the root element.
59. Bubbling and Tunneling.
A. Bubbling: When the events are raised form the innermost element in the visual tree and comes up towards the root element, is called as bubbling.
Tunneling: It is the opposite process of Bubbling where the events fired by the root element goes down towards the last child element control.

60. Resource Dictionary, Static Resources and Dynamic Resources.
A. Static and Dynamic resources are used for binding the resources to the control objects. 
The main difference between StaticResource and DynamicResource is that how the resource is retrieved elements. If the resource is StaticResource, it will be retrieved only once by the element whoe is referencing it  and it will be used for all the resources. While the DynamicResource gets its value each time they reference to the objects. So StaticResource is faster than the DynamicResource , because StaticResource needs to get the value only once while the DynamicResource  needs each time to get it.
61. What is Prism? 
A. Prism is the framework or the set of guidelines which is used to develop the WPF desktop application as well as the Silverlight Rich Internet applications. So it’s a kind of Design pattern to Develop the XMAL based application. It also used to develop the Windows 7 applications. Prism mainly helps to design the loosely coupled components which can be easily integrated with the other components of the overall application. Prism mainly used to build the composite applications which need various other components to be integrated. 
Prism mainly guides of creating the applications using the Model-View-ViewModel (MVVM) model, Managed Extensibility Framework (MEF), and navigation in the application.
To use the Prism framework, we need to use their library called as Prism Library. So prism Library is the inbuilt set of components which can be used in developing the WPF and Silverlight applications.

62. Dependency Injection, Event Aggregator.
EventAggregator : It is the utility service which contains the events and allows the decouple the publisher and subscriber so that they can be buildup independently. Decouple is primarily useful when a new module needs to be added or removed or modified. The new module can be added as per the event fired and defined in the shell.

63. Shell, Bootstrapper and Region Managers
A. Bootstrapper:- An utility in WPF engine which is mainly responsible for the initialization of the application by using the composite application library. By using the bootstrapper we can find out how the components of the application are wired up in the composite application library. The bootstrapper responsibility to create the Shell or main window. Composite application library has the default abstract class UnityBootstrapper which actually handles the initialization.

Region and Region Managers: This is concept of Prism framework. We define the region through XAML code and once a region is defined, automatically it will be registered with the RegionManager. Actually the Bootstrapper registers a service called the RegionManager at run time. RegionManager is a dictionary where the key is name of the region. The value of the key is the reference of the IRegion interface. RegionAdapter is used to create the instance reference of the IRegion interface.

64. What are MEF and Unity?
A.  The MEF (Managed Extensibility Framework) is the new concept in .net 4.0. It is used to create the lightweight and extensible applications to create Managed Extensibility Framework. It is not only allows the extension but also reused within the application. Extension can be easily encapsulating the code using the MEF.

65. How to navigate to another page?
A. There is a class NavigationService which can be used for navigation of the WPF window:
this.NavigationService.GoForward();
//or
this.NavigationService.Navigate("MysecondPage.xaml")

MS SQL Sever

What is a MS SQL? MS SQL is short for Microsoft SQL Server. It is a relational web hosting database that is used to store web site information like blog posts or user information. MS SQL is the most popular type of database on Windows servers. It is not free but it has many advanced features that make it suitable for businesses.

• SQL stands for Structured Query Language
• SQL lets you access and manipulate databases
• SQL is an ANSI (American National Standards Institute) standard

What Can SQL do?

• SQL can execute queries against a database
• SQL can retrieve data from a database
• SQL can insert records in a database
• SQL can update records in a database
• SQL can delete records from a database
• SQL can create new databases
• SQL can create new tables in a database
• SQL can create stored procedures in a database
• SQL can create views in a database
• SQL can set permissions on tables, procedures, and views

RDBMS

RDBMS stands for Relational Database Management System.
RDBMS is the basis for SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.
The data in RDBMS is stored in database objects called tables.
A table is a collection of related data entries and it consists of columns and rows.

 

What is MS SQL capable of?

In basic terms, an MS SQL database is capable of storing any type of that you want. It will let you quickly store and retrieve information and multiple web site visitors can use it at one time. You will use SQL statements to accomplish all of this. In more technical terms, most versions of MS SQL have the following features:

• Buffer management
• Logging and Transaction
• Concurrency and locking
• Replication services
• Analysis services
• Notification services
• Integration services
• Full text search service
• Stored procedures
• Triggers
• Views
• Sub-SELECTs (i.e. nested SELECTs)

What is MS SQL used for?

MS SQL is the database of choice for web applications on a Windows platform (using .NET or ASP). These languages make is extremely easy to connect to a MS SQL database. It is also used for many popular content management systems and other scripts.

PHP Date and Time

Dates are so much part of everyday life that it becomes easy to work with them without thinking. PHP also provides powerful tools for date arithmetic that make manipulating dates easy.

Getting the Time Stamp with time():

PHP's time() function gives you all the information that you need about the current date and time. It requires no arguments but returns an integer.
The integer returned by time() represents the number of seconds elapsed since midnight GMT on January 1, 1970. This moment is known as the UNIX epoch, and the number of seconds that have elapsed since then is referred to as a time stamp.

<?php print time(); ?>

It will produce following result:

948316201

This is something difficult to understand. But PHP offers excellent tools to convert a time stamp into a form that humans are comfortable with.

Converting a Time Stamp with getdate():

The function getdate() optionally accepts a time stamp and returns an associative array containing information about the date. If you omit the time stamp, it works with the current time stamp as returned by time().
Following table lists the elements contained in the array returned by getdate().

Key	Description	Example
seconds	Seconds past the minutes (0-59)	20
minutes	Minutes past the hour (0 - 59)	29
hours	Hours of the day (0 - 23)	22
mday	Day of the month (1 - 31)	11
wday	Day of the week (0 - 6)	4
mon	Month of the year (1 - 12)	7
year	Year (4 digits)	1997
yday	Day of year ( 0 - 365 )	19
weekday	Day of the week	Thursday
month	Month of the year	January
0	Timestamp	948370048

Now you have complete control over date and time. You can format this date and time in whatever format you wan.

Example:

Try out following example

<?php $date_array = getdate(); foreach ( $date_array as $key => $val ) { print "$key = $val<br />"; } $formated_date = "Today's date: "; $formated_date .= $date_array[mday] . "/"; $formated_date .= $date_array[mon] . "/"; $formated_date .= $date_array[year]; print $formated_date; ?>

It will produce following result:

seconds = 27 minutes = 25 hours = 11 mday = 12 wday = 6 mon = 5 year = 2007 yday = 131 weekday = Saturday month = May 0 = 1178994327 Today's date: 12/5/2007

Converting a Time Stamp with date():

The date() function returns a formatted string representing a date. You can exercise an enormous amount of control over the format that date() returns with a string argument that you must pass to it.

date(format,timestamp)

The date() optionally accepts a time stamp if ommited then current date and time will be used. Any other data you include in the format string passed to date() will be included in the return value.
Following table lists the codes that a format string can contain:

Format	Description	Example
a	'am' or 'pm' lowercase	pm
A	'AM' or 'PM' uppercase	PM
d	Day of month, a number with leading zeroes	20
D	Day of week (three letters)	Thu
F	Month name	January
h	Hour (12-hour format - leading zeroes)	12
H	Hour (24-hour format - leading zeroes)	22
g	Hour (12-hour format - no leading zeroes)	12
G	Hour (24-hour format - no leading zeroes)	22
i	Minutes ( 0 - 59 )	23
j	Day of the month (no leading zeroes	20
l (Lower 'L')	Day of the week	Thursday
L	Leap year ('1' for yes, '0' for no)	1
m	Month of year (number - leading zeroes)	1
M	Month of year (three letters)	Jan
r	The RFC 2822 formatted date	Thu, 21 Dec 2000 16:01:07 +0200
n	Month of year (number - no leading zeroes)	2
s	Seconds of hour	20
U	Time stamp	948372444
y	Year (two digits)	06
Y	Year (four digits)	2006
z	Day of year (0 - 365)	206
Z	Offset in seconds from GMT	+5

Example:

Try out following example

<?php print date("m/d/y G.i:s<br>", time()); print "Today is "; print date("j of F Y, \a\\t g.i a", time()); ?>

It will produce following result:

01/20/00 13.27:55
Today is 20 of January 2000, at 1.27 pm

PHP Bugs Debugging

Programs rarely work correctly the first time. Many things can go wrong in your program that cause the PHP interpreter to generate an error message. You have a choice about where those error messages go. The messages can be sent along with other program output to the web browser. They can also be included in the web server error log.
To make error messages display in the browser, set the display_errors configuration directive to On. To send errors to the web server error log, set log_errors to On. You can set them both to On if you want error messages in both places.
PHP defines some constants you can use to set the value of error_reporting such that only errors of certain types get reported: E_ALL (for all errors except strict notices), E_PARSE (parse errors), E_ERROR (fatal errors), E_WARNING (warnings), E_NOTICE (notices), and E_STRICT (strict notices).
While writing your PHP program, it is a good idea to use PHP-aware editors like BBEdit or Emacs. One of the speical special features of these editors is syntax highlighting. It changes the color of different parts of your program based on what those parts are. For example, strings are pink, keywords such as if and while are blue, comments are grey, and variables are black.
Another feature is quote and bracket matching, which helps to make sure that your quotes and brackets are balanced. When you type a closing delimiter such as }, the editor highlights the opening { that it matches.
There are following points which need to be verfied while debugging your program.

• Missing Semicolons - Every PHP statement ends with a semicolon (;). PHP doesn't stop reading a statement until it reaches a semicolon. If you leave out the semicolon at the end of a line, PHP continues reading the statement on the following line.
• Not Enough Equal Signs - When you ask whether two values are equal in a comparison statement, you need two equal signs (==). Using one equal sign is a common mistake.
• Misspelled Variable Names - If you misspelled a variable then PHP understands it as a new variable. Remember: To PHP, $test is not the same variable as $Test.
• Missing Dollar Signs - A missing dollar sign in a variable name is really hard to see, but at least it usually results in an error message so that you know where to look for the problem.
• Troubling Quotes - You can have too many, too few, or the wrong kind of quotes. So check for a balanced number of quotes.
• Missing Parentheses and curly brackets - They should always be in pairs.
• Array Index - All the arrays should start from zero instead of 1.

Moreoever, handle all the errors properly and direct all trace messages into system log file so that if any problem happens then it will be logged into system log file and you will be able to debug that problem.

PHP Error and Exception Handling

Error handling is the process of catching errors raised by your program and then taking appropriate action. If you would handle errors properly then it may lead to many unforeseen consequences.
Its very simple in PHP to handle an errors.

Using die() function:

While wirting your PHP program you should check all possible error condition before going ahead and take appropriate action when required.
Try following example without having /tmp/test.xt file and with this file.

<?php if(!file_exists("/tmp/test.txt")) { die("File not found"); } else { $file=fopen("/tmp/test.txt","r"); print "Opend file sucessfully"; } // Test of the code here. ?>

This way you can write an efficient code. Using abive technique you can stop your program whenever it errors out and display more meaningful and user friendly meassage.

Defining Custom Error Handling Function:

You can write your own function to handling any error. PHP provides you a framwork to define error handling function.
This function must be able to handle a minimum of two parameters (error level and error message) but can accept up to five parameters (optionally: file, line-number, and the error context):

Syntax

error_function(error_level,error_message, error_file,error_line,error_context);

 

Parameter	Description
error_level	Required - Specifies the error report level for the user-defined error. Must be a value number.
error_message	Required - Specifies the error message for the user-defined error
error_file	Optional - Specifies the filename in which the error occurred
error_line	Optional - Specifies the line number in which the error occurred
error_context	Optional - Specifies an array containing every variable and their values in use when the error occurred

Possible Error levels

These error report levels are the different types of error the user-defined error handler can be used for. These values cab used in combination using | operator

Value	Constant	Description
1	E_ERROR	Fatal run-time errors. Execution of the script is halted
2	E_WARNING	Non-fatal run-time errors. Execution of the script is not halted
4	E_PARSE	Compile-time parse errors. Parse errors should only be generated by the parser.
8	E_NOTICE	Run-time notices. The script found something that might be an error, but could also happen when running a script normally
16	E_CORE_ERROR	Fatal errors that occur during PHP's initial startup.
32	E_CORE_WARNING	Non-fatal run-time errors. This occurs during PHP's initial startup.
256	E_USER_ERROR	Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error()
512	E_USER_WARNING	Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error()
1024	E_USER_NOTICE	User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error()
2048	E_STRICT	Run-time notices. Enable to have PHP suggest changes to your code which will ensure the best interoperability and forward compatibility of your code.
4096	E_RECOVERABLE_ERROR	Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler())
8191	E_ALL	All errors and warnings, except level E_STRICT (E_STRICT will be part of E_ALL as of PHP 6.0)

All the above error level can be set using following PHP built-in library function where level cab be any of the value defined in above table.

int error_reporting ( [int $level] )

Following is the way you can create one error handling function:

<?php function handleError($errno, $errstr,$error_file,$error_line) { echo "<b>Error:</b> [$errno] $errstr - $error_file:$error_line"; echo "<br />"; echo "Terminating PHP Script"; die(); } ?>

Once you define your custom error handler you need to set it using PHP built-in library set_error_handler function. Now lets examine our example by calling a function which does not exist.

<?php error_reporting( E_ERROR ); function handleError($errno, $errstr,$error_file,$error_line) { echo "<b>Error:</b> [$errno] $errstr - $error_file:$error_line"; echo "<br />"; echo "Terminating PHP Script"; die(); } //set error handler set_error_handler("handleError"); //trigger error myFunction(); ?>

Exceptions Handling:

PHP 5 has an exception model similar to that of other programming languages. Exceptions are important and provides a better control over error handling.
Lets explain thre new keyword related to exceptions.

• Try - A function using an exception should be in a "try" block. If the exception does not trigger, the code will continue as normal. However if the exception triggers, an exception is "thrown".
• Throw - This is how you trigger an exception. Each "throw" must have at least one "catch".
• Catch - - A "catch" block retrieves an exception and creates an object containing the exception information.

When an exception is thrown, code following the statement will not be executed, and PHP will attempt to find the first matching catch block. If an exception is not caught, a PHP Fatal Error will be issued with an "Uncaught Exception ...

• An exception can be thrown, and caught ("catched") within PHP. Code may be surrounded in a try block.
• Each try must have at least one corresponding catch block. Multiple catch blocks can be used to catch different classes of exeptions.
• Exceptions can be thrown (or re-thrown) within a catch block.

Example:

Following is the piece of code, copy and paste this code into a file and verify the result.

<?php try { $error = 'Always throw this error'; throw new Exception($error); // Code following an exception is not executed. echo 'Never executed'; } catch (Exception $e) { echo 'Caught exception: ', $e->getMessage(), "\n"; } // Continue execution echo 'Hello World'; ?>

In the above example $e->getMessage function is uded to get error message. There are following functions which can be used from Exception class.

• getMessage()- message of exception
• getCode() - code of exception
• getFile() - source filename
• getLine() - source line
• getTrace() - n array of the backtrace()
• getTraceAsString() - formated string of trace

Creating Custom Exception Handler:

You can define your own custome excpetion handler. Use following function to set a user-defined exception handler function.

string set_exception_handler ( callback $exception_handler )

Here exception_handler is the name of the function to be called when an uncaught exception occurs. This function must be defined before calling set_exception_handler().

Example:

<?php
function exception_handler($exception) {
  echo "Uncaught exception: " , $exception->getMessage(), "\n";
}

set_exception_handler('exception_handler');

throw new Exception('Uncaught Exception');

echo "Not Executed\n";
?>

PHP -Regular Expressions

Regular expressions are nothing more than a sequence or pattern of characters itself. They provide the foundation for pattern-matching functionality.
Using regular expression you can search a particular string inside a another string, you can replace one string by another string and you can split a string into many chunks.
PHP offers functions specific to two sets of regular expression functions, each corresponding to a certain type of regular expression. You can use any of them based on your comfort.

• POSIX Regular Expressions
• PERL Style Regular Expressions

POSIX Regular Expressions:

The structure of a POSIX regular expression is not dissimilar to that of a typical arithmetic expression: various elements (operators) are combined to form more complex expressions.
The simplest regular expression is one that matches a single character, such as g, inside strings such as g, haggle, or bag.
Lets give explaination for few concepts being used in POSIX regular expression. After that we will introduce you wih regular expression related functions.

Brackets

Brackets ([]) have a special meaning when used in the context of regular expressions. They are used to find a range of characters.

Expression	Description
[0-9]	It matches any decimal digit from 0 through 9.
[a-z]	It matches any character from lowercase a through lowercase z.
[A-Z]	It matches any character from uppercase A through uppercase Z.
[a-Z]	It matches any character from lowercase a through uppercase Z.

The ranges shown above are general; you could also use the range [0-3] to match any decimal digit ranging from 0 through 3, or the range [b-v] to match any lowercase character ranging from b through v.

Quantifiers:

The frequency or position of bracketed character sequences and single characters can be denoted by a special character. Each pecial character having a specific connotation. The +, *, ?, {int. range}, and $ flags all follow a character sequence.

Expression	Description
p+	It matches any string containing at least one p.
p*	It matches any string containing zero or more p's.
p?	It matches any string containing zero or more p's. This is just an alternative way to use p*.
p{N}	It matches any string containing a sequence of N p's
p{2,3}	It matches any string containing a sequence of two or three p's.
p{2, }	It matches any string containing a sequence of at least two p's.
p$	It matches any string with p at the end of it.
^p	It matches any string with p at the beginning of it.

Examples:

Following examples will clear your concepts about matching chracters.

Expression	Description
[^a-zA-Z]	It matches any string not containing any of the characters ranging from a through z and A through Z.
p.p	It matches any string containing p, followed by any character, in turn followed by another p.
^.{2}$	It matches any string containing exactly two characters.
<b>(.*)</b>	It matches any string enclosed within <b> and </b>.
p(hp)*	It matches any string containing a p followed by zero or more instances of the sequence hp.

Predefined Character Ranges

For your programming convenience several predefined character ranges, also known as character classes, are available. Character classes specify an entire range of characters, for example, the alphabet or an integer set:

Expression	Description
[[:alpha:]]	It matches any string containing alphabetic characters aA through zZ.
[[:digit:]]	It matches any string containing numerical digits 0 through 9.
[[:alnum:]]	It matches any string containing alphanumeric characters aA through zZ and 0 through 9.
[[:space:]]	It matches any string containing a space.

PHP's Regexp POSIX Functions

PHP currently offers seven functions for searching strings using POSIX-style regular expressions:

Function	Description
ereg()	The ereg() function searches a string specified by string for a string specified by pattern, returning true if the pattern is found, and false otherwise.
ereg_replace()	The ereg_replace() function searches for string specified by pattern and replaces pattern with replacement if found.
eregi()	The eregi() function searches throughout a string specified by pattern for a string specified by string. The search is not case sensitive.
eregi_replace()	The eregi_replace() function operates exactly like ereg_replace(), except that the search for pattern in string is not case sensitive.
split()	The split() function will divide a string into various elements, the boundaries of each element based on the occurrence of pattern in string.
spliti()	The spliti() function operates exactly in the same manner as its sibling split(), except that it is not case sensitive.
sql_regcase()	The sql_regcase() function can be thought of as a utility function, converting each character in the input parameter string into a bracketed expression containing two characters.

PERL Style Regular Expressions:

Perl-style regular expressions are similar to their POSIX counterparts. The POSIX syntax can be used almost interchangeably with the Perl-style regular expression functions. In fact, you can use any of the quantifiers introduced in the previous POSIX section.
Lets give explaination for few concepts being used in PERL regular expressions. After that we will introduce you wih regular expression related functions.

Metacharacters

A metacharacter is simply an alphabetical character preceded by a backslash that acts to give the combination a special meaning.
For instance, you can search for large money sums using the '\d' metacharacter: /([\d]+)000/, Here \d will search for any string of numerical character.
Following is the list of metacharacters which can be used in PERL Style Regular Expressions.

Character Description . a single character \s a whitespace character (space, tab, newline) \S non-whitespace character \d a digit (0-9) \D a non-digit \w a word character (a-z, A-Z, 0-9, _) \W a non-word character [aeiou] matches a single character in the given set [^aeiou] matches a single character outside the given set (foo|bar|baz) matches any of the alternatives specified

Modifiers

Several modifiers are available that can make your work with regexps much easier, like case sensitivity, searching in multiple lines etc.

Modifier Description i Makes the match case insensitive m Specifies that if the string has newline or carriage return characters, the ^ and $ operators will now match against a newline boundary, instead of a string boundary o Evaluates the expression only once s Allows use of . to match a newline character x Allows you to use white space in the expression for clarity g Globally finds all matches cg Allows a search to continue even after a global match fails

PHP's Regexp PERL Compatible Functions

PHP offers following functions for searching strings using Perl-compatible regular expressions:

Function	Description
preg_match()	The preg_match() function searches string for pattern, returning true if pattern exists, and false otherwise.
preg_match_all()	The preg_match_all() function matches all occurrences of pattern in string.
preg_replace()	The preg_replace() function operates just like ereg_replace(), except that regular expressions can be used in the pattern and replacement input parameters.
preg_split()	The preg_split() function operates exactly like split(), except that regular expressions are accepted as input parameters for pattern.
preg_grep()	The preg_grep() function searches all elements of input_array, returning all elements matching the regexp pattern.
preg_ quote()	Quote regular expression characters