Web Dev Interview Questions

Interview questions for Web developer position

  1. What’s the difference between primary key and unique key?
  2. The Perl script on the site is working slow. What’s your plan of attack?
  3. Name several reasons why a Web site would not work entirely.
  4. Write an SQL statement that would select only the customers who made multiple orders within a single week.
  5. What version control systems do you use?
  6. How do you configure the maximum number of processes in Apache?
  7. How much memory do you need for Web server app? Describe your logic of calculating this number.
  8. What are response codes 302 and 303?
  9. How do you delete all files with file extension temp recursively on a Linux box?
  10. What Perl tools do you use for coding, testing, debugging?
  11. Do you use DHTML and JavaScript? Describe the projects you’ve used them in.

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PHP interview questions, Part 1

  1. What are the differences between Get and post methods in form submitting, give the case where we can use get and we can use post methods?
  2. Who is the father of PHP and explain the changes in PHP versions?
  3. How can we submit a form without a submit button?
  4. In how many ways we can retrieve the date in the result set of mysql using PHP?
  5. What is the difference between mysql_fetch_object and mysql_fetch_array?
  6. What is the difference between $message and $$message?
  7. How can we extract string ‘abc.com ‘ from a string ‘http://info@abc.com’ using regular expression of PHP?
  8. How can we create a database using PHP and mysql?
  9. What are the differences between require and include, include_once?
  10. Can we use include (”abc.PHP”) two times in a PHP page “makeit.PHP”?
  11. What are the different tables present in mysql, which type of table is generated when we are creating a table in the following syntax: create table employee(eno int(2),ename varchar(10)) ?
  12. Functions in IMAP, POP3 AND LDAP?
  13. How can I execute a PHP script using command line?
  14. Suppose your Zend engine supports the mode <? ?> Then how can u configure your PHP Zend engine to support <?PHP ?> mode ?
  15. Shopping cart online validation i.e. how can we configure Paypal, etc.?
  16. What is meant by nl2br()?
  17. Draw the architecture of Zend engine?
  18. What are the current versions of apache, PHP, and mysql?
  19. What are the reasons for selecting lamp (linux, apache, mysql, PHP) instead of combination of other software programmes, servers and operating systems?
  20. How can we encrypt and decrypt a data present in a mysql table using mysql?
  21. How can we encrypt the username and password using PHP?
  22. What are the features and advantages of object-oriented programming?
  23. What are the differences between procedure-oriented languages and object-oriented languages?
  24. What is the use of friend function?
  25. What are the differences between public, private, protected, static, transient, final and volatile?
  26. What are the different types of errors in PHP?
  27. What is the functionality of the function strstr and stristr?
  28. What are the differences between PHP 3 and PHP 4 and PHP 5?
  29. How can we convert asp pages to PHP pages?
  30. What is the functionality of the function htmlentities?
  31. How can we get second of the current time using date function?
  32. How can we convert the time zones using PHP?
  33. What is meant by urlencode and urldocode?
  34. What is the difference between the functions unlink and unset?
  35. How can we register the variables into a session?
  36. How can we get the properties (size, type, width, height) of an image using PHP image functions?
  37. How can we get the browser properties using PHP?
  38. What is the maximum size of a file that can be uploaded using PHP and how can we change this?
  39. How can we increase the execution time of a PHP script?
  40. How can we take a backup of a mysql table and how can we restore it. ?
  41. How can we optimize or increase the speed of a mysql select query?
  42. How many ways can we get the value of current session id?
  43. How can we destroy the session, how can we unset the variable of a session?
  44. How can we destroy the cookie?
  45. How many ways we can pass the variable through the navigation between the pages?
  46. What is the difference between ereg_replace() and eregi_replace()?
  47. What are the different functions in sorting an array?
  48. How can we know the count/number of elements of an array?
  49. What is the PHP predefined variable that tells the What types of images that PHP supports?
  50. How can I know that a variable is a number or not using a JavaScript?
  51. List out some tools through which we can draw E-R diagrams for mysql.
  52. How can I retrieve values from one database server and store them in other database server using PHP?
  53. List out the predefined classes in PHP?
  54. How can I make a script that can be bilanguage (supports English, German)?
  55. What are the difference between abstract class and interface?
  56. How can we send mail using JavaScript?

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ASP.NET questions, part 1

  1. Explain the differences between Server-side and Client-side code? Server side scripting means that all the script will be executed by the server and interpreted as needed. ASP doesn’t have some of the functionality like sockets, uploading, etc. For these you have to make a custom components usually in VB or VC++. Client side scripting means that the script will be executed immediately in the browser such as form field validation, clock, email validation, etc. Client side scripting is usually done in VBScript or JavaScript. Download time, browser compatibility, and visible code - since JavaScript and VBScript code is included in the HTML page, then anyone can see the code by viewing the page source. Also a possible security hazards for the client computer.
  2. What type of code (server or client) is found in a Code-Behind class? C#
  3. Should validation (did the user enter a real date) occur server-side or client-side? Why? Client-side validation because there is no need to request a server side date when you could obtain a date from the client machine.
  4. What does the "EnableViewState" property do? Why would I want it on or off? Enable ViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip without requiring you to write any code. This feature is not free however, since the state of a control is passed to and from the server in a hidden form field. You should be aware of when ViewState is helping you and when it is not. For example, if you are binding a control to data on every round trip (as in the datagrid example in tip #4), then you do not need the control to maintain it’s view state, since you will wipe out any re-populated data in any case. ViewState is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.
  5. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other? Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist accros the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive. Response.Dedirect() :client know the physical loation (page name and query string as well). Context.Items loses the persisitance when nevigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
  6. Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component? When to Use Web Services:
    • Communicating through a Firewall When building a distributed application with 100s/1000s of users spread over multiple locations, there is always the problem of communicating between client and server because of firewalls and proxy servers. Exposing your middle tier components as Web Services and invoking the directly from a Windows UI is a very valid option.
    • Application Integration When integrating applications written in various languages and running on disparate systems. Or even applications running on the same platform that have been written by separate vendors.
    • Business-to-Business Integration This is an enabler for B2B intergtation which allows one to expose vital business processes to authorized supplier and customers. An example would be exposing electronic ordering and invoicing, allowing customers to send you purchase orders and suppliers to send you invoices electronically.
    • Software Reuse This takes place at multiple levels. Code Reuse at the Source code level or binary componet-based resuse. The limiting factor here is that you can reuse the code but not the data behind it. Webservice overcome this limitation. A scenario could be when you are building an app that aggregates the functionality of serveral other Applicatons. Each of these functions could be performed by individual apps, but there is value in perhaps combining the the multiple apps to present a unifiend view in a Portal or Intranet.
    • When not to use Web Services: Single machine Applicatons When the apps are running on the same machine and need to communicate with each other use a native API. You also have the options of using component technologies such as COM or .NET Componets as there is very little overhead.
    • Homogeneous Applications on a LAN If you have Win32 or Winforms apps that want to communicate to their server counterpart. It is much more efficient to use DCOM in the case of Win32 apps and .NET Remoting in the case of .NET Apps.
  7. Let’s say I have an existing application written using Visual Studio (VBInterDevand this application utilizes WindowsCOM+ transaction services. How would you approach migrating this application to .NET?
  8. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset? In ADO, the in-memory representation of data is the recordset. In ADO.NET, it is the dataset. There are important differences between them.
    • A recordset looks like a single table. If a recordset is to contain data from multiple database tables, it must use a JOIN query, which assembles the data from the various database tables into a single result table. In contrast, a dataset is a collection of one or more tables. The tables within a dataset are called data tables; specifically, they are DataTable objects. If a dataset contains data from multiple database tables, it will typically contain multiple DataTable objects. That is, each DataTable object typically corresponds to a single database table or view. In this way, a dataset can mimic the structure of the underlying database. A dataset usually also contains relationships. A relationship within a dataset is analogous to a foreign-key relationship in a database —that is, it associates rows of the tables with each other. For example, if a dataset contains a table about investors and another table about each investor’s stock purchases, it could also contain a relationship connecting each row of the investor table with the corresponding rows of the purchase table. Because the dataset can hold multiple, separate tables and maintain information about relationships between them, it can hold much richer data structures than a recordset, including self-relating tables and tables with many-to-many relationships.
    • In ADO you scan sequentially through the rows of the recordset using the ADO MoveNext method. In ADO.NET, rows are represented as collections, so you can loop through a table as you would through any collection, or access particular rows via ordinal or primary key index. DataRelation objects maintain information about master and detail records and provide a method that allows you to get records related to the one you are working with. For example, starting from the row of the Investor table for "Nate Sun," you can navigate to the set of rows of the Purchase table describing his purchases. A cursor is a database element that controls record navigation, the ability to update data, and the visibility of changes made to the database by other users. ADO.NET does not have an inherent cursor object, but instead includes data classes that provide the functionality of a traditional cursor. For example, the functionality of a forward-only, read-only cursor is available in the ADO.NET DataReader object. For more information about cursor functionality, see Data Access Technologies.
    • Minimized Open Connections: In ADO.NET you open connections only long enough to perform a database operation, such as a Select or Update. You can read rows into a dataset and then work with them without staying connected to the data source. In ADO the recordset can provide disconnected access, but ADO is designed primarily for connected access. There is one significant difference between disconnected processing in ADO and ADO.NET. In ADO you communicate with the database by making calls to an OLE DB provider. In ADO.NET you communicate with the database through a data adapter (an OleDbDataAdapter, SqlDataAdapter, OdbcDataAdapter, or OracleDataAdapter object), which makes calls to an OLE DB provider or the APIs provided by the underlying data source. The important difference is that in ADO.NET the data adapter allows you to control how the changes to the dataset are transmitted to the database — by optimizing for performance, performing data validation checks, or adding any other extra processing. Data adapters, data connections, data commands, and data readers are the components that make up a .NET Framework data provider. Microsoft and third-party providers can make available other .NET Framework data providers that can be integrated into Visual Studio.
    • Sharing Data Between Applications. Transmitting an ADO.NET dataset between applications is much easier than transmitting an ADO disconnected recordset. To transmit an ADO disconnected recordset from one component to another, you use COM marshalling. To transmit data in ADO.NET, you use a dataset, which can transmit an XML stream.
    • Richer data types.COM marshalling provides a limited set of data types — those defined by the COM standard. Because the transmission of datasets in ADO.NET is based on an XML format, there is no restriction on data types. Thus, the components sharing the dataset can use whatever rich set of data types they would ordinarily use.
    • Performance. Transmitting a large ADO recordset or a large ADO.NET dataset can consume network resources; as the amount of data grows, the stress placed on the network also rises. Both ADO and ADO.NET let you minimize which data is transmitted. But ADO.NET offers another performance advantage, in that ADO.NET does not require data-type conversions. ADO, which requires COM marshalling to transmit records sets among components, does require that ADO data types be converted to COM data types.
    • Penetrating Firewalls.A firewall can interfere with two components trying to transmit disconnected ADO recordsets. Remember, firewalls are typically configured to allow HTML text to pass, but to prevent system-level requests (such as COM marshalling) from passing.
  9. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines? The Application_Start event is guaranteed to occur only once throughout the lifetime of the application. It’s a good place to initialize global variables. For example, you might want to retrieve a list of products from a database table and place the list in application state or the Cache object. SessionStateModule exposes both Session_Start and Session_End events.
  10. If I’m developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users?
  11. What are ASP.NET Web Forms? How is this technology different than what is available though ASP? Web Forms are the heart and soul of ASP.NET. Web Forms are the User Interface (UI) elements that give your Web applications their look and feel. Web Forms are similar to Windows Forms in that they provide properties, methods, and events for the controls that are placed onto them. However, these UI elements render themselves in the appropriate markup language required by the request, e.g. HTML. If you use Microsoft Visual Studio .NET, you will also get the familiar drag-and-drop interface used to create your UI for your Web application.
  12. How does VB.NET/C# achieve polymorphism? By using Abstract classes/functions.
  13. Can you explain what inheritance is and an example of when you might use it? Inheritance is a fundamental feature of an object oriented system and it is simply the ability to inherit data and functionality from a parent object. Rather than developing new objects from scratch, new code can be based on the work of other programmers, adding only new features that are needed.
  14. How would you implement inheritance using VB.NET/C#? When we set out to implement a class using inheritance, we must first start with an existing class from which we will derive our new subclass. This existing class, or base class, may be part of the .NET system class library framework, it may be part of some other application or .NET assembly, or we may create it as part of our existing application. Once we have a base class, we can then implement one or more subclasses based on that base class. Each of our subclasses will automatically have all of the methods, properties, and events of that base class ? including the implementation behind each method, property, and event. Our subclass can add new methods, properties, and events of its own - extending the original interface with new functionality. Additionally, a subclass can replace the methods and properties of the base class with its own new implementation - effectively overriding the original behavior and replacing it with new behaviors. Essentially inheritance is a way of merging functionality from an existing class into our new subclass. Inheritance also defines rules for how these methods, properties, and events can be merged.

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Perl interview questions

  1. What arguments do you frequently use for the Perl interpreter and what do they mean?
  2. What does the command ‘use strict’ do and why should you use it?
  3. What do the symbols $ @ and % mean when prefixing a variable?
  4. What elements of the Perl language could you use to structure your code to allow for maximum re-use and maximum readability?
  5. What are the characteristics of a project that is well suited to Perl?
  6. Why do you program in Perl?
  7. Explain the difference between my and local.
  8. Explain the difference between use and require.
  9. What’s your favorite module and why?
  10. What is a hash?
  11. Write a simple (common) regular expression to match an IP address, e-mail address, city-state-zipcode combination.
  12. What purpose does each of the following serve: -w, strict, -T ?
  13. What is the difference between for & foreach, exec & system?
  14. Where do you go for Perl help?
  15. Name an instance where you used a CPAN module.
  16. How do you open a file for writing?
  17. How would you replace a char in string and how do you store the number of replacements?
  18. When would you not use Perl for a project?

Check out Perl Monks for discussion of the questions and related Perl interview issues. Check RegExpLib for regular expression samples.


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Basic .NET and ASP.NET interview questions

Submitter said questions were asked in a US company hiring a Web developer.

  1. Explain the .NET architecture.
  2. How many languages .NET is supporting now? - When .NET was introduced it came with several languages. VB.NET, C#, COBOL and Perl, etc. The site DotNetLanguages.Net says 44 languages are supported.
  3. How is .NET able to support multiple languages? - a language should comply with the Common Language Runtime standard to become a .NET language. In .NET, code is compiled to Microsoft Intermediate Language (MSIL for short). This is called as Managed Code. This Managed code is run in .NET environment. So after compilation to this IL the language is not a barrier. A code can call or use a function written in another language.
  4. How ASP .NET different from ASP? - Scripting is separated from the HTML, Code is compiled as a DLL, these DLLs can be executed on the server.
  5. Resource Files: How to use the resource files, how to know which language to use?
  6. What is smart navigation? - The cursor position is maintained when the page gets refreshed due to the server side validation and the page gets refreshed.
  7. What is view state? - The web is stateless. But in ASP.NET, the state of a page is maintained in the in the page itself automatically. How? The values are encrypted and saved in hidden controls. this is done automatically by the ASP.NET. This can be switched off / on for a single control
  8. Explain the life cycle of an ASP .NET page.
  9. How do you validate the controls in an ASP .NET page? - Using special validation controls that are meant for this. We have Range Validator, Email Validator.
  10. Can the validation be done in the server side? Or this can be done only in the Client side? - Client side is done by default. Server side validation is also possible. We can switch off the client side and server side can be done.
  11. How to manage pagination in a page? - Using pagination option in DataGrid control. We have to set the number of records for a page, then it takes care of pagination by itself.
  12. What is ADO .NET and what is difference between ADO and ADO.NET? - ADO.NET is stateless mechanism. I can treat the ADO.Net as a separate in-memory database where in I can use relationships between the tables and select insert and updates to the database. I can update the actual database as a batch.

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