Hi friends here some of Interview Questions
which were asked to me during interview
I hope it will helpful to you...
What is a CAPTCHA and when do you use it?
CAPTCHA is the short form of Completely
Automated Public Turing Test. It’s a step taken to ensure that a feature is not
abused in a way it’s not meant to be used. We use CAPTCHAS for general form
submissions, registrations, user generated content and so on to prevent spam
bots from clogging up the system or spamming.
What is the current version of PHP and MYSQL?
Their current versions are
PHP is 5.4.1 (As of this writing. Make sure
you know the current version when you go in for your interview)
MySQL- 5.5.23
Can you tell me the difference between
include and require functions?
Both these functions differ in how they
handle failures that occur.
Suppose a file is not found by the include()
function, then it will simply give a warning and script execution will not be
interrupted.
However, if a file is not found using a
require() function, it will throw up a fatal warning and stop the script
execution.
What the difference is between get and post
method in HTTP?
GET Method:
- All the name value pairs are submitted as a query string in URL. It's not secured as it is visible in plain text format in
the Location bar of the web browser.
- As the data transfers through address bar (URL) there are some
restrictions in using space, some characters like ampersand (&) etc.
in the GET method of posting data. We have to take special care for
encoding data if such special characters are present.
- Length of the string is restricted.
- If method is not mentioned in the Form tag, this is the default
method used.
- If get method is used and if the page is refreshed it would not
prompt before the request is submitted again.
- One can store the name value pairs as bookmark and directly be used
while sharing with others - example search results.
- Data is always submitted in the form of text
- If the response of the page is always same for the posted query then
use GET example database searches
POST Method:
- 1. All the name value pairs are submitted in the Message Body of the
request.
- 2. Length of the string (amount of data submitted) is not
restricted.
- 3. Post Method is secured because Name-Value pairs cannot be seen in
location bar of the web browser.
- 4. If post method is used and if the page is refreshed it
would prompt before the request is resubmitted.
- 5. If the service associated with the processing of a form has side
effects (for example, modification of a database or subscription to a
service), the method should be POST.
- 6. Data is submitted in the form as specified in enctype attribute of
form tag and thus files can be used in FileUpload input box.
Is it possible to create a database using PHP
and MySQL?
Yes. We can create a database using the function
mysql_create_db(?<Insert database name here>?).
Is it possible to know details about the
browser being used to view a PHP website?
Yes. We can use the get_browser() function
to get the details of the browser a
user is using. This information is usually found inside
the browscap.ini file.
String Concatenation -
There are two different ways to combine
variables in PHP. Let’s take an example.
$var1 = “Hello”;
$var2 = “World”;
We can combine it using the two codes below
$var3 = $var1.$var2; and
$var3 = “$var1$var2″;
Method Definitions:-
The set of common methods for HTTP/1.1 is
defined below. Although this set can be expanded, additional methods cannot be
assumed to share the same semantics for separately extended clients and
servers.
Safe and Idempotent
Methods
- OPTIONS
- GET
- HEAD
- POST
- PUT
- DELETE
- TRACE
- CONNECT
What does setAutoCommit(false) do?
A JDBC connection is created in auto-commit
mode by default. This means that each individual SQL statement is treated as a
transaction and will be automatically committed as soon as it is executed. If
you require two or more statements to be grouped into a transaction then you
need to disable auto-commit mode using below command
con.setAutoCommit(false);
Once auto-commit mode is disabled, no SQL
statements will be committed until you explicitly call the commit method. A
Simple transaction with use of autocommit flag is demonstrated below.
con.setAutoCommit(false);
PreparedStatement updateStmt =
con.prepareStatement( "UPDATE EMPLOYEE SET SALARY = ? WHERE EMP_NAME LIKE?");
updateStmt.setInt(1, 5000); updateSales.setString(2, "Jack");
updateStmt.executeUpdate();
updateStmt.setInt(1, 6000); updateSales.setString(2, "Tom");
updateStmt.executeUpdate();
con.commit();
con.setAutoCommit(true);
What is Connection pooling? What are the
advantages of using a connection pool?
Connection Pooling is a technique used for
sharing the server resources among requested clients. It was pioneered by
database vendors to allow multiple clients to share a cached set of connection
objects that provides access to a database.
Getting connection and disconnecting are
costly operation, which affects the application performance, so we should avoid
creating multiple connections during multiple database interactions.
A pool contains set of Database connections
which are already connected, and any client who wants to use it can take it
from pool and when done with using it can be returned back to the pool.
Apart from performance this also saves you
resources as there may be limited database connections available for your
application.
What is a stored procedure? How to call
stored procedure using JDBC API?
Stored procedure is a group of SQL statements
that forms a logical unit and performs a particular task.
Stored Procedures are used to encapsulate a
set of operations or queries to execute on database. Stored procedures can be
compiled and executed with different parameters and results and may have any
combination of input/output parameters. Stored procedures can be called using
CallableStatement class in JDBC API.
Below code snippet shows how this can be
achieved.
CallableStatement cs =
con.prepareCall("{call MY_STORED_PROC_NAME}");
ResultSet rs = cs.executeQuery();
What are the types of statements in JDBC?
The JDBC API has 3 Interfaces,
1. Statement
2. PreparedStatement,
3. CallableStatement
The key features of these are as follows:
Statement
This interface is used for executing a static
SQL statement and returning the results it produces.
The object of Statement class can be created
using Connection.createStatement() method.
PreparedStatement
A SQL statement is pre-compiled and stored in
a PreparedStatement object.
This object can then be used to efficiently
execute this statement multiple times.
The object of PreparedStatement class can be
created using Connection.prepareStatement() method. This extends Statement
interface.
CallableStatement
This interface is used to execute SQL stored
procedures.
This extends PreparedStatement interface.
The object of CallableStatement class can be
created using Connection.prepareCall() method.
What does Class.forName() method do?
Method forName() is a static method of
java.lang.Class. This can be used to dynamically load a class at run-time.
Class.forName() loads the class if it’s not already loaded. It also executes
the static block of loaded class. Then this method returns an instance of the
loaded class. So a call to Class.forName('MyClass') is going to do following
- Load the class MyClass.
- Execute any static block code of MyClass.
- Return an instance of MyClass.
JDBC Driver loading using Class.forName is a
good example of best use of this method. The driver loading is done like this
Class.forName("org.mysql.Driver");
All JDBC Drivers have a static block that
registers itself with DriverManager and DriverManager has static initializer
method registerDriver() which can be called in a static blocks of Driver
class. A MySQL JDBC Driver has a static initializer which looks like this:
static {
try {
java.sql.DriverManager.registerDriver(new Driver());
} catch (SQLException E) {
throw new RuntimeException("Can't register driver!");
}
}
Class.forName() loads driver class and
executes the static block and the Driver registers itself with the
DriverManager.
Best of Luck....
By
Swapnil Sonar
