Thursday, May 30, 2013

Top 100 PHP interview questions and answers

Questions 1:  Who is the father of PHP ?
Answers 1: Rasmus Lerdorf is known as the father of PHP.

Questions 2: What is the difference between $name and $$name? 
Answers 2: $name is variable where as $$name is reference variable
like $name=sonia and $$name=singh so $sonia value is singh.

Questions 3: How can we submit a form without a submit button? 
Answer 3: Java script submit() function is used for submit form without submit button
on click call document.formname.submit()

Questions 4: In how many ways we can retrieve the data in the result set of MySQL using PHP? 
Answer 4: We can do it by 4 Ways
1. mysql_fetch_row. , 2. mysql_fetch_array , 3. mysql_fetch_object
4. mysql_fetch_assoc

Questions 5: What is the difference between mysql_fetch_object and mysql_fetch_array? 
Answers 5: mysql_fetch_object() is similar tomysql_fetch_array(), with one difference -
an object is returned, instead of an array. Indirectly, that means that
you can only access the data by the field names, and not by their
offsets (numbers are illegal property names).

Questions 6: What are the differences between Get and post methods. 
Answers 6: There are some defference between GET and POST method
1. GET Method have some limit like only 2Kb data able to send for request
But in POST method unlimited data can we send
2. when we use GET method requested data show in url but
Not in POST method so POST method is good for send sensetive request

Questions 7: How can we extract string " " from a string "" using regular expression of PHP? 
Answers 7: preg_match("/^http:\/\/.+@(.+)$/","",$matches);
echo $matches[1];

Questions 8: How can we create a database using PHP and MySQL? 
Answers 8: We can create MySQL database with the use of mysql_create_db("Database Name")

Questions 9: What are the differences between require and include? 
Answers 9: Both include and require used to include a file but when included file not found Include send Warning where as Require send Fatal Error.

Questions 10: Can we use include ("xyz.PHP") two times in a PHP page "index.PHP"? 
Answers 10: Yes we can use include("xyz.php") more than one time in any page. but it create
a problem when xyz.php file contain some functions declaration then error will come
for already declared function in this file else not a problem like if you want to show
same content two time in page then must include it two time not a problem

Questions 11: What are the different tables(Engine) present in MySQL, which one is default? 
Answers 11: Following tables (Storage Engine) we can create
1. MyISAM(The default storage engine IN MYSQL Each MyISAM table is stored on
disk in three files. The files have names that begin with the table name and have
an extension to indicate the file type. An .frm file stores the table format. The data
file has an .MYD (MYData) extension. The index file has an .MYI (MYIndex)
extension. )
2. InnoDB(InnoDB is a transaction-safe (ACID compliant) storage engine for
MySQL that has commit, rollback, and crash-recovery capabilities to protect user
3. Merge
4. Heap (MEMORY)(The MEMORY storage engine creates tables with contents
that are stored in memory. Formerly, these were known as HEAP tables. MEMORY
is the preferred term, although HEAP remains supported for backward
compatibility. )
5. BDB (BerkeleyDB)(Sleepycat Software has provided MySQL with the Berkeley
DB transactional storage engine. This storage engine typically is called BDB for
short. BDB tables may have a greater chance of surviving crashes and are also
capable of COMMIT and ROLLBACK operations on transactions)
7. FEDERATED (It is a storage engine that accesses data in tables of remote
databases rather than in local tables. )
8. ARCHIVE (The ARCHIVE storage engine is used for storing large amounts of
data without indexes in a very small footprint. )
9. CSV (The CSV storage engine stores data in text files using comma-separated
values format.)
10. BLACKHOLE (The BLACKHOLE storage engine acts as a "black hole" that
accepts data but throws it away and does not store it. Retrievals always return an
empty result)

Questions 12: What is use of header() function in php ?
Answers 12: The header() function sends a raw HTTP header to a client.We can use herder()
function for redirection of pages. It is important to notice that header() must
be called before any actual output is seen..

Questions 13: How can I execute a PHP script using command line?
Answers 13: Just run the PHP CLI (Command Line Interface) program and
provide the PHP script file name as the command line argument.

Questions 14: Suppose your Zend engine supports the mode <? ?> Then how can u
configure your PHP Zend engine to support <?PHP ?> mode ?
Answers 14: In php.ini file: set short_open_tag=on to make PHP support

Questions 15: Shopping cart online validation i.e. how can we configure Paypal, etc.?
Answers 15: Nothing more we have to do only redirect to the payPal url after submit all information needed by paypal like amount,adresss etc.

Questions 16: What is meant by nl2br()?
Answers 16: Inserts HTML line breaks (<BR />) before all newlines in a string.

Questions 17: What is htaccess? Why do we use this and Where?
Answers 17: .htaccess files are configuration files of Apache Server which provide
a way to make configuration changes on a per-directory basis. A file,
containing one or more configuration directives, is placed in a particular
document directory, and the directives apply to that directory, and all
subdirectories thereof.

Questions 18: How we get IP address of client, previous reference page etc ?
Answers 18: By using $_SERVER['REMOTE_ADDR'],$_SERVER['HTTP_REFERER'] etc.

Questions 19: What are the reasons for selecting lamp (Linux, apache, MySQL,PHP) instead of combination of other software programs, servers and operating systems?
Answers 19: All of those are open source resource. Security of Linux is very very more than windows. Apache is a better server that IIS both in
functionality and security. MySQL is world most popular open source
database. PHP is more faster that asp or any other scripting language.

Questions 20: How can we encrypt and decrypt a data present in a MySQL table using MySQL?
Answers 20: AES_ENCRYPT () and AES_DECRYPT ()

Questions 21: How can we encrypt the username and password using PHP?
Answers 21: The functions in this section perform encryption and decryption, and compression and uncompression:
encryption decryption
ENCRYPT() Not available
MD5() Not available
OLD_PASSWORD() Not available
PASSWORD() Not available
SHA() or SHA1() Not available

Questions 22: What are the features and advantages of object-oriented programming?
Answers 22: One of the main advantages of OO programming is its ease of
modification; objects can easily be modified and added to a system there
by reducing maintenance costs. OO programming is also considered to be
better at modeling the real world than is procedural programming. It
allows for more complicated and flexible interactions. OO systems are
also easier for non-technical personnel to understand and easier for
them to participate in the maintenance and enhancement of a system
because it appeals to natural human cognition patterns.
For some systems, an OO approach can speed development time since many
objects are standard across systems and can be reused. Components that
manage dates, shipping, shopping carts, etc. can be purchased and easily
modified for a specific system

Questions 23: What are the differences between procedure-oriented languages and object-oriented languages?
Answers 23: There are lot of difference between procedure language and object oriented like below
1>Procedure language easy for new developer but complex to understand whole
software as compare to object oriented model
2>In Procedure language it is difficult to use design pattern mvc , Singleton
pattern etc but in OOP you we able to develop design pattern
3>IN OOP language we able to ree use code like Inheritance ,polymorphism etc
but this type of thing not available in procedure language on that our Fonda use

Questions 24: What is the use of friend function?
Answers 24: Sometimes a function is best shared among a number of different
classes. Such functions can be declared either as member functions of
one class or as global functions. In either case they can be set to be
friends of other classes, by using a friend specifier in the class that
is admitting them. Such functions can use all attributes of the class
which names them as a friend, as if they were themselves members of that
A friend declaration is essentially a prototype for a member function,
but instead of requiring an implementation with the name of that class
attached by the double colon syntax, a global function or member
function of another class provides the match.

Questions 25: What are the differences between public, private, protected, static, transient, final and volatile?
Answer 25:
Public: Public declared items can be accessed everywhere.
Protected: Protected limits access to inherited and parent
classes (and to the class that defines the item).
Private: Private limits visibility only to the class that defines
the item.
Static: A static variable exists only in a local function scope,
but it does not lose its value when program execution leaves this scope.
Final: Final keyword prevents child classes from overriding a
method by prefixing the definition with final. If the class itself is
being defined final then it cannot be extended.
transient: A transient variable is a variable that may not
be serialized.
volatile: a variable that might be concurrently modified by multiple
threads should be declared volatile. Variables declared to be volatile
will not be optimized by the compiler because their value can change at
any time.

Questions 26: What are the different types of errors in PHP?
Answer 26: Three are three types of errors:1. Notices: These are trivial,
non-critical errors that PHP encounters while executing a script – for
example, accessing a variable that has not yet been defined. By default,
such errors are not displayed to the user at all – although, as you will
see, you can change this default behavior.2. Warnings: These are more serious
errors – for example, attempting
to include() a file which does not exist. By default, these errors are
displayed to the user, but they do not result in script termination.3. Fatal errors:
These are critical errors – for example,
instantiating an object of a non-existent class, or calling a
non-existent function. These errors cause the immediate termination of
the script, and PHP's default behavior is to display them to the user
when they take place.

Questions 27: What is the functionality of the function strstr and stristr?
Answers 27: strstr Returns part of string from the first occurrence of needle(sub string that we finding out ) to the end of string.
$email= '';
$domain = strstr($email, '@');
echo $domain; // prints
here @ is the needle
stristr is case-insensitive means able not able to diffrenciate between a and A

Questions 28: What are the differences between PHP 3 and PHP 4 and PHP 5?
Answer 28: There are lot of difference among these three version of php
1>Php3 is oldest version after that php4 came and current version is php5
(php5.3) where php6 have to come
2>Difference mean oldest version have less functionality as compare to new one
like php5 have all OOPs concept now where as php3 was pure procedural language
constructive like C
In PHP5 1. Implementation of exceptions and exception handling
2. Type hinting which allows you to force the type of a specific argument
3. Overloading of methods through the __call function
4. Full constructors and destructors etc through a __constuctor and __destructor
5. __autoload function for dynamically including certain include files depending on
the class you are trying to create.
6 Finality : can now use the final keyword to indicate that a method cannot be
overridden by a child. You can also declare an entire class as final which prevents
it from having any children at all.
7 Interfaces & Abstract Classes
8 Passed by Reference :
9 An __clone method if you really want to duplicate an object
10 Numbers of Functions Deprecated in php 5.x like
ereg,ereg_replace,magic_quotes_runtime, session_register,register_globals,
split(), call_user_method() etc

Questions 29: How can we convert asp pages to PHP pages?
Answer 29: there are lots of tools available for asp to PHP conversion. you can
search Google for that. the best one is available at

Questions 30: What is the functionality of the function htmlentities?
Answer 30: Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, exceptwith htmlentities(), all characters which have HTML character entity
equivalents are translated into these entities.

Questions 31: How can we get second of the current time using date function?
Answer 31: $second = date("s");

Questions 32: How can we convert the time zones using PHP?
Answer 32: By using date_default_timezone_get and date_default_timezone_set function on PHP 5.1.0
// Discover what 8am in Tokyo relates to on the East
Coast of the US
// Set the default timezone to Tokyo time:
// Now generate the timestamp for that particular
timezone, on Jan 1st, 2000
$stamp = mktime(8, 0, 0, 1, 1, 2000);
// Now set the timezone back to US/Eastern
// Output the date in a standard format (RFC1123), this
will print:
// Fri, 31 Dec 1999 18:00:00 EST
echo '<p>', date(DATE_RFC1123, $stamp) ,'</p>';?>

Questions 33: What is meant by urlencode and urldocode?
Answer 33: URLencode returns a string in which all non-alphanumeric characters
except -_. have been replaced with a percent ( %)
sign followed by two hex digits and spaces encoded as plus (+)
signs. It is encoded the same way that the posted data from a WWW form
is encoded, that is the same way as in
application/x-www-form-urlencoded media type.
urldecode decodes any %##
encoding in the given string.

Questions 34: What is the difference between the functions unlink and unset?
Answer 34: unlink() deletes the given file from the file system. unset() makes a variable undefined.

Questions 35: How can we register the variables into a session?
Answer 35: $_SESSION['name'] = "sonia";

Questions 36: How can we get the properties (size, type, width, height) of an image using PHP image functions?
Answer 36:
To know the Image size use getimagesize () function
To know the Image type use exif_imagetype () function
To know the Image width use imagesx () function
To know the Image height use imagesy() function

Questions 37: How can we get the browser properties using PHP?
Answer 37: By using $_SERVER['HTTP_USER_AGENT'] variable.

Questions 38: What is the maximum size of a file that can be uploaded using PHP and how can we change this?
Answer 38: By default the maximum size is 2MB. and we can change the following
setup at php.ini file upload_max_filesize = 2M

Questions 39: How can we increase the execution time of a PHP script?
Answer 39: by changing the following setup at php.ini file max_execution_time = 30; Maximum execution time of each script, in seconds

Questions 40: How can we take a backup of a MySQL table and how can we restore it.?
Answer 40:
To backup: BACKUP TABLE tbl_name[,tbl_name…] TO
RESTORE TABLE tbl_name[,tbl_name…] FROM
'/path/to/backup/directory'mysqldump: Dumping Table Structure and DataUtility
to dump a database or a collection of database for backup or
for transferring the data to another SQL server (not necessarily a MySQL
server). The dump will contain SQL statements to create the table and/or
populate the table.
-t, –no-create-info
Don't write table creation information (the CREATE TABLE statement).
-d, –no-data
Don't write any row information for the table. This is very useful if
you just want to get a dump of the structure for a table!

Questions 41: How can we optimize or increase the speed of a MySQL select query?
Answer 41: first of all instead of using select * from table1, use select
column1, column2, column3.. from table1
Look for the opportunity to introduce index in the table you are
use limit keyword if you are looking for any specific number of
rows from the result set.

Questions 42: How many ways can we get the value of current session id?
Answer 42: session_id() returns the session id for the current session.

Questions 43: How can we destroy the session, how can we unset the variable of a session?
Answer 43: session_unregister — Unregister a global variable from the current session, session_unset — Free all session variables

Questions 44: How can we set and destroy the cookie in php?
Answer 44:
By using setcookie(name, value, expire, path, domain); function we can set the
cookie in php ;
Set the cookies in past for destroy. like
setcookie("user", "sonia", time()+3600); for set the cookie
setcookie("user", "", time()-3600); for destroy or delete the cookies;

Questions 45: How many ways we can pass the variable through the navigation between the pages?
Answer 45:GET/QueryString, POST

Questions 46: What is the difference between ereg_replace() and eregi_replace()?
Answer 46:
eregi_replace() function is identical to ereg_replace() except that
this ignores case distinction when matching alphabetic
characters.eregi_replace() function is identical to ereg_replace()
except that this ignores case distinction when matching alphabetic

Questions 47: What are the different functions in sorting an array?
Answer 47:
Sort(), arsort(),
asort(), ksort(),
natsort(), natcasesort(),
rsort(), usort(),
array_multisort(), and

Questions 48: How can we know the count/number of elements of an array?
Answer 48: 2 ways
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)

Questions 49: what is session_set_save_handler in PHP?
Answer 49: session_set_save_handler() sets the user-level session storage functions
which are used for storing and retrieving data associated with a session. This is
most useful when a storage method other than those supplied by PHP sessions is
preferred. i.e. Storing the session data in a local database.

Questions 50: How can I know that a variable is a number or not using a JavaScript?
Answer 50: bool is_numeric ( mixed var)
Returns TRUE if var is a number or a numeric string, FALSE otherwise.or use
isNaN(mixed var)The isNaN() function is used to check if a value is not a number.

Questions 51: List out some tools through which we can draw E-R diagrams for mysql.
Answer 51:Case Studio, Smart Draw

Questions 52: How can I retrieve values from one database server and store them in other database server using PHP?
Answer 52:
we can always fetch from one database and rewrite to another. here
is a nice solution of it.$db1 = mysql_connect("host","user","pwd")
mysql_select_db("db1", $db1);
$res1 = mysql_query("query",$db1);$db2 = mysql_connect("host","user","pwd")
mysql_select_db("db2", $db2);
$res2 = mysql_query("query",$db2);At this point you can only fetch records from
you previous ResultSet,
i.e $res1 – But you cannot execute new query in $db1, even if you
supply the link as because the link was overwritten by the new at this point
the following script will fail
$res3 = mysql_query("query",$db1); //this will failSo how to solve that?
take a look below.
$db1 = mysql_connect("host","user","pwd")
mysql_select_db("db1", $db1);
$res1 = mysql_query("query",$db1);
$db2 = mysql_connect("host","user","pwd", true)
mysql_select_db("db2", $db2);
$res2 = mysql_query("query",$db2);
So mysql_connect has another optional boolean parameter which
indicates whether a link will be created or not. as we connect to the
$db2 with this optional parameter set to 'true', so both link will
remain live.
now the following query will execute successfully.
$res3 = mysql_query("query",$db1);

Questions 53: List out the predefined classes in PHP?
Answer 53:

Questions 54: How can I make a script that can be bi-language (supports English, German)?
Answer 54:
You can maintain two separate language file for each of the
language. all the labels are putted in both language files as variables
and assign those variables in the PHP source. on runtime choose the
required language option.

Questions 55: What are the difference between abstract class and interface?
Answer 55:
Abstract class: abstract classes are the class where one or more
methods are abstract but not necessarily all method has to be abstract.
Abstract methods are the methods, which are declare in its class but notdefine. The definition of those methods must be in its extending class.Interface:
Interfaces are one type of class where all the methods are
abstract. That means all the methods only declared but not defined. All
the methods must be define by its implemented class.

Questions 56: How can we send mail using JavaScript?
Answer 56:
JavaScript does not have any networking capabilities as it is
designed to work on client site. As a result we can not send mails using
JavaScript. But we can call the client side mail protocol mailto
via JavaScript to prompt for an email to send. this requires the client
to approve it.

Questions 57: How can we repair a MySQL table?
Answer 57:
The syntex for repairing a MySQL table is
This command will repair the table specified if the quick is given the
MySQL will do a repair of only the index tree if the extended is given
it will create index row by row

Questions 58: What are the advantages of stored procedures, triggers, indexes?
Answer 58:
A stored procedure is a set of SQL commands that can be compiled and
stored in the server. Once this has been done, clients don't need to
keep re-issuing the entire query but can refer to the stored procedure.
This provides better overall performance because the query has to be
parsed only once, and less information needs to be sent between the
server and the client. You can also raise the conceptual level by having
libraries of functions in the server. However, stored procedures of
course do increase the load on the database server system, as more of
the work is done on the server side and less on the client (application)
side.Triggers will also be implemented. A trigger is effectively a type of
stored procedure, one that is invoked when a particular event occurs.
For example, you can install a stored procedure that is triggered each
time a record is deleted from a transaction table and that stored
procedure automatically deletes the corresponding customer from a
customer table when all his transactions are deleted.Indexes are used to find rows
with specific column values quickly.
Without an index, MySQL must begin with the first row and then read
through the entire table to find the relevant rows. The larger the
table, the more this costs. If the table has an index for the columns in
question, MySQL can quickly determine the position to seek to in the
middle of the data file without having to look at all the data. If a
table has 1,000 rows, this is at least 100 times faster than reading
sequentially. If you need to access most of the rows, it is faster to
read sequentially, because this minimizes disk seeks.

Questions 59: What is the maximum length of a table name, database name, and fieldname in MySQL?
Answer 59: The following table describes the maximum length for each type of identifier.
Identifier Maximum Length(bytes)
Database 64
Table 64
Column 64
Index 64
Alias 255

There are some restrictions on the characters that may appear in identifiers:

Questions 60: How many values can the SET function of MySQL take?
Answer 60:
MySQL set can take zero or more values but at the maximum it can
take 64 values

Questions 61: What are the other commands to know the structure of table using MySQL commands except explain command?
Answer 61: describe Table-Name;

Questions 62: How many tables will create when we create table, what are they?
Answer 62:
The '.frm' file stores the table definition.
The data file has a '.MYD' (MYData) extension.
The index file has a '.MYI' (MYIndex) extension,

Questions 63: What is the purpose of the following files having extensions 1).frm 2).myd 3).myi? What do these files contain?
Answer 63: In MySql, the default table type is MyISAM.Each MyISAM table is stored on disk in three files. The files have names
that begin with the table name and have an extension to indicate the
file type.
The '.frm' file stores the table definition.
The data file has a '.MYD' (MYData) extension.
The index file has a '.MYI' (MYIndex) extension,

Questions 64: What is maximum size of a database in MySQL?
Answer 64: If the operating system or filesystem places a limit on the number
of files in a directory, MySQL is bound by that constraint.The efficiency of the
operating system in handling large numbers of
files in a directory can place a practical limit on the number of tables
in a database. If the time required to open a file in the directory
increases significantly as the number of files increases, database
performance can be adversely affected.
The amount of available disk space limits the number of tables.
MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM
storage engine in MySQL 3.23, the maximum table size was increased to
65536 terabytes (2567 – 1 bytes). With this larger allowed table size,
the maximum effective table size for MySQL databases is usually
determined by operating system constraints on file sizes, not by MySQL
internal limits.The InnoDB storage engine maintains InnoDB tables within a
that can be created from several files. This allows a table to exceed
the maximum individual file size. The tablespace can include raw disk
partitions, which allows extremely large tables. The maximum tablespace
size is 64TB.
The following table lists some examples of operating system file-size
limits. This is only a rough guide and is not intended to be definitive.
For the most up-to-date information, be sure to check the documentation
specific to your operating system.Operating System File-size LimitLinux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 filesystem) 4TB
Solaris 9/10 16TB
NetWare w/NSS filesystem 8TB
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
MacOS X w/ HFS+ 2TB

Questions 65: Give the syntax of Grant and Revoke commands?
Answer 65: The generic syntax for grant is as following
> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY
now rights can be
a) All privileges
b) combination of create, drop, select, insert, update and delete etc.We can grant
rights on all databse by using *.* or some specific
database by database.* or a specific table by database.table_name
username@hotsname can be either username@localhost, username@hostname
and username@%
where hostname is any valid hostname and % represents any name, the *.*
any condition
password is simply the password of userThe generic syntax for revoke is as
> REVOKE [rights] on [database/s] FROM [username@hostname]
now rights can be as explained above
a) All privileges
b) combination of create, drop, select, insert, update and delete etc.
username@hotsname can be either username@localhost, username@hostname
and username@%
where hostname is any valid hostname and % represents any name, the *.*
any condition

Questions 66: Explain Normalization concept?
Answer 66:
The normalization process involves getting our data to conform to
three progressive normal forms, and a higher level of normalization
cannot be achieved until the previous levels have been achieved (there
are actually five normal forms, but the last two are mainly academic and
will not be discussed).First Normal FormThe First Normal Form (or 1NF) involves
removal of redundant data
from horizontal rows. We want to ensure that there is no duplication of
data in a given row, and that every column stores the least amount of
information possible (making the field atomic).Second Normal FormWhere the
First Normal Form deals with redundancy of data across a
horizontal row, Second Normal Form (or 2NF) deals with redundancy of
data in vertical columns. As stated earlier, the normal forms are
progressive, so to achieve Second Normal Form, your tables must already
be in First Normal Form.Third Normal Form
I have a confession to make; I do not often use Third Normal Form. In
Third Normal Form we are looking for data in our tables that is not
fully dependant on the primary key, but dependant on another value in
the table

Questions 67: How can we find the number of rows in a table using MySQL?
Answer 67: Use this for mysql
>SELECT COUNT(*) FROM table_name;

Questions 68: How can we find the number of rows in a result set using PHP?
Answer 68:
$result = mysql_query($sql, $db_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";

Questions 69: How many ways we can we find the current date using MySQL?
Answer 69:
for time use

Questions 70: What are the advantages and disadvantages of Cascading Style Sheets?
Answer 70: External Style SheetsAdvantagesCan control styles for multiple documents at
once. Classes can be created for use on multiple HTML element types in many documents.
Selector and grouping methods can be used to apply styles under complex
contextsDisadvantagesAn extra download is required to import style information
for each
document The rendering of the document may be delayed until the external
style sheet is loaded Becomes slightly unwieldy for small quantities of
style definitionsEmbedded Style Sheets
Classes can be created for use on multiple tag types in the document.
Selector and grouping methods can be used to apply styles under complex
contexts. No additional downloads necessary to receive style information
This method can not control styles for multiple documents at once
Inline Styles
Useful for small quantities of style definitions. Can override other
style specification methods at the local level so only exceptions need
to be listed in conjunction with other style methods
Does not distance style information from content (a main goal of
SGML/HTML). Can not control styles for multiple documents at once.
Author can not create or control classes of elements to control multiple
element types within the document. Selector grouping methods can not be
used to create complex element addressing scenarios

Questions 71: What type of inheritance that PHP supports?
Answer 71: In PHP an extended class is always dependent on a single base class,
that is, multiple inheritance is not supported. Classes are extended
using the keyword 'extends'.

Questions 72: What is the difference between Primary Key and Unique key?
Answer 72:
Primary Key: A column in a table whose values uniquely identify the
rows in the table. A primary key value cannot be NULL.
Unique Key: Unique Keys are used to uniquely identify each row in the
table. There can be one and only one row for each unique key value. So
NULL can be a unique key.There can be only one primary key for a table but there
can be more than one unique for a table.

Question 73: what is garbage collection? default time ? refresh time?
Answer 73: Garbage Collection is an automated part of PHP , If the Garbage Collection process
 runs, it then analyzes any files in the /tmp for any session files that have not been
  accessed in a certain amount of time and physically deletes them. Garbage
 Collection process only runs in the default session save directory, which is /tmp. If
you opt to save your sessions in a different directory, the Garbage Collection
process will ignore it. the Garbage Collection process does not differentiate
between which sessions belong to whom when run. This is especially important
note on shared web servers. If the process is run, it deletes ALL files that have not
been accessed in the directory. There are 3 PHP.ini variables, which deal with the
garbage collector: PHP ini value name default session.gc_maxlifetime 1440
seconds or 24 minutes session.gc_probability 1 session.gc_divisor 100

Questions 74: What are the advantages/disadvantages of MySQL and PHP?
Answer 74: Both of them are open source software (so free of cost), support
cross platform. php is faster then ASP and JSP.

Questions 75: What is the difference between GROUP BY and ORDER BY in Sql?
Answer 75:
ORDER BY [col1],[col2],…,[coln]; Tels DBMS according to what columns
it should sort the result. If two rows will hawe the same value in col1
it will try to sort them according to col2 and so on.
GROUP BY [col1],[col2],…,[coln]; Tels DBMS to group results with same value of
column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if
you want to count all items in group, sum all values or view average

Questions 76: What is the difference between char and varchar data types?
Answer 76: Set char to occupy n bytes and it will take n bytes even if u r
storing a value of n-m bytes
Set varchar to occupy n bytes and it will take only the required space
and will not use the n bytes
eg. name char(15) will waste 10 bytes if we store 'romharshan', if each char
takes a byte
eg. name varchar(15) will just use 5 bytes if we store 'romharshan', if each
char takes a byte. rest 10 bytes will be free.

Questions 77: What is the functionality of md5 function in PHP?
Answer 77:
Calculate the md5 hash of a string. The hash is a 32-character
hexadecimal number. I use it to generate keys which I use to identify
users etc. If I add random no techniques to it the md5 generated nowwill be totally different for the same string I am using.

Questions 78: How can I load data from a text file into a table?
Answer 78:you can use LOAD DATA INFILE file_name; syntax to load data
from a text file. but you have to make sure thata) data is delimited
b) columns and data matched correctly

Questions 79: How can we know the number of days between two given dates usingMySQL?
Answer 79:
SELECT DATEDIFF("2007-03-07","2005-01-01");

Questions 80: How can we know the number of days between two given dates usingPHP?
Answer 80:
$date1 = date("Y-m-d");
$date2 = "2006-08-15";
$days = (strtotime($date1) - strtotime($date2)) / (60 * 60 * 24);

Questions 81: How we load all classes that placed in different directory in one PHP File , means how to do auto load classes
Answer 81:
by using spl_autoload_register('autoloader::funtion');
Like below
class autoloader
public static function moduleautoloader($class)
$path = $_SERVER['DOCUMENT_ROOT'] . "/modules/{$class}.php";
if (is_readable($path)) require $path;
public static function daoautoloader($class)
$path = $_SERVER['DOCUMENT_ROOT'] . "/dataobjects/{$class}.php";
if (is_readable($path)) require $path;
public static function includesautoloader($class)
$path = $_SERVER['DOCUMENT_ROOT'] . "/includes/{$class}.php";
if (is_readable($path)) require $path;

Questions 82: How many types of Inheritances used in PHP and how we achieve it
Answer 82: As far PHP concern it only support single Inheritance in scripting.
we can also use interface to achieve multiple inheritance.

Questions 83: PHP how to know user has read the email?
Answers 83: Using Disposition-Notification-To: in mailheader we can get read receipt.
Add the possibility to define a read receipt when sending an email.
Itâ€TMs quite straightforward, just edit email.php, and add this at vars definitions:
var $readReceipt = null;
And then, at †̃createHeaderâ€TM function add:
if (!empty($this->readReceipt)) {
$this->__header .= †̃Disposition-Notification-To: †̃ . $this-
>__formatAddress($this->readReceipt) . $this->_newLine;

Questions 84: What are default session time and path?
Answers 84: default session time in PHP is 1440 seconds or 24 minutes Default session save path id temporary folder /tmp

Questions 85: how to track user logged out or not? when user is idle ?
Answers 85: By checking the session variable exist or not while loading th page. As the session
will exist longer as till browser closes. The default behaviour for sessions is to
keep a session open indefinitely and only to expire a session when the browser is
closed. This behaviour can be changed in the php.ini file by altering the line
session.cookie_lifetime = 0 to a value in seconds. If you wanted the session to
finish in 5 minutes you would set this to session.cookie_lifetime = 300 and restart
your httpd server.

Questions 86: how to track no of user logged in ?
Answers 86: whenever a user logs in track the IP, userID etc..and store it in a DB with a active
flag while log out or sesion expire make it inactive. At any time by counting the
no: of active records we can get the no: of visitors.

Questions 87: in PHP for pdf which library used?
Answers 87: The PDF functions in PHP can create PDF files using the PDFlib library With version 6, PDFlib offers an object-oriented API for PHP 5 in addition to the function-
oriented API for PHP 4. There is also the » Panda module. FPDF is a PHP class
which allows to generate PDF files with pure PHP, that is to say without using the
PDFlib library. F from FPDF stands for Free: you may use it for any kind of usage
and modify it to suit your needs. FPDF requires no extension (except zlib to
activate compression and GD for GIF support) and works with PHP4 and PHP5.

Questions 88: for image work which library?
Answers 88: we will need to compile PHP with the GD library of image functions for this to
work. GD and PHP may also require other libraries, depending on which image
formats you want to work with.

Questions 89: what is design pattern? singleton pattern?
Answers 89: A design pattern is a general reusable solution to a commonly occurring problem
in software design.
The Singleton design pattern allows many parts of a program to share a single
resource without having to work out the details of the sharing themselves.

Questions 90: what are magic methods?
Answers 90: Magic methods are the members functions that is available to all the instance of
class Magic methods always starts with "__". Eg. __construct All magic methods
needs to be declared as public To use magic method they should be defined within
the class or program scope Various Magic Methods used in PHP 5 are:
__construct() __destruct() __set() __get() __call() __toString() __sleep()
__wakeup() __isset() __unset() __autoload() __clone()

Questions 91: what is magic quotes?
Answers 91: Magic Quotes is a process that automagically escapes ncoming data to the PHP
script. Itâ€TMs preferred to code with magic quotes off and to instead escape the
data at runtime, as needed. This feature has been DEPRECATED as of PHP 5.3.0
and REMOVED as of PHP 6.0.0. Relying on this feature is highly discouraged.

Questions 92: what is cross site scripting? SQL injection?
Answers 92: Cross-site scripting (XSS) is a type of computer security vulnerability typically
found in web applications which allow code injection by malicious web users into
the web pages viewed by other users. Examples of such code include HTML code
and client-side scripts. SQL injection is a code injection technique that exploits a
security vulnerability occurring in the database layer of an application. The
vulnerability is present when user input is either incorrectly filtered for string
literal escape characters embedded in SQL statements or user input is not strongly
typed and thereby unexpectedly executed

Questions 93: what is URL rewriting?
Answers 93: Using URL rewriting we can convert dynamic URl to static URL Static URLs are
known to be better than Dynamic URLs because of a number of reasons 1. Static
URLs typically Rank better in Search Engines. 2. Search Engines are known to
index the content of dynamic pages a lot slower compared to static pages. 3.
Static URLs are always more friendlier looking to the End Users. along with this we
can use URL rewriting in adding variables [cookies] to the URL to handle the

Questions 94: what is the major php security hole? how to avoid?
Answers 94:
1. Never include, require, or otherwise open a file with a filename based on user
input, without thoroughly checking it first.
2. Be careful with eval() Placing user-inputted values into the eval() function canbe extremely dangerous. You essentially give the malicious user the ability to
execute any command he or she wishes!
3. Be careful when using register_globals = ON It was originally designed to make
programming in PHP easier (and that it did), but misuse of it often led to security
4. Never run unescaped queries
5. For protected areas, use sessions or validate the login every time.
6. If you donâ€TMt want the file contents to be seen, give the file a .php extension.

Questions 95: whether PHP supports Microsoft SQL server ?
Answers 95: The SQL Server Driver for PHP v1.0 is designed to enable reliable, scalable
integration with SQL Server for PHP applications deployed on the Windows
platform. The Driver for PHP is a PHP 5 extension that allows the reading and
writing of SQL Server data from within PHP scripts. using MSSQL or ODBC
modules we can access Microsoft SQL server.

Questions 96: what is MVC? why its been used?
Answers 96: Model-view-controller (MVC) is an architectural pattern used in software
engineering. Successful use of the pattern isolates business logic from user
interface considerations, resulting in an application where it is easier to modify
either the visual appearance of the application or the underlying business rules
without affecting the other. In MVC, the model represents the information (the
data) of the application; the view corresponds to elements of the user interface
such as text, checkbox items, and so forth; and the controller manages the
communication of data and the business rules used to manipulate the data to and
from the model. WHY ITS NEEDED IS 1 Modular separation of function 2 Easier to
maintain 3 View-Controller separation means:
A — Tweaking design (HTML) without altering code B — Web design staff can
modify UI without understanding code

Questions 97: what is framework? how it works? what is advantage?
Answers 97: In general, a framework is a real or conceptual structure intended to serve as a
support or guide for the building of something that expands the structure into
something useful. Advantages : Consistent Programming Model Direct Support for
Security Simplified Development Efforts Easy Application Deployment and

Questions 98: what is CURL?
Answers 98: CURL means Client URL Library
curl is a command line tool for transferring files with URL syntax, supporting FTP,
supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based
upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM,
Negotiate, kerberos…), file transfer resume, proxy tunneling and a busload of
other useful tricks.
CURL allows you to connect and communicate to many different types of servers
with many different types of protocols. libcurl currently supports the http, https,
ftp, gopher, telnet, dict, file, and ldap protocols. libcurl also supports HTTPS
certificates, HTTP POST, HTTP PUT, FTP uploading (this can also be done with
PHPâ€TMs ftp extension), HTTP form based upload, proxies, cookies, and
user+password authentication.

Questions 99: what is PDO ?
Answers 99: The PDO ( PHP Data Objects ) extension defines a lightweight, consistent interface
for accessing databases in PHP. if you are using the PDO API, you could switch the
database server you used, from say PgSQL to MySQL, and only need to make
minor changes to your PHP code.
While PDO has its advantages, such as a clean, simple, portable API but its main
disadvantage is that it doesn't allow you to use all of the advanced features that
are available in the latest versions of MySQL server. For example, PDO does not
allow you to use MySQL's support for Multiple Statements.
Just need to use below code for connect mysql using PDO
try {
$dbh = new PDO("mysql:host=$hostname;dbname=databasename", $username,
$sql = "SELECT * FROM employee";
foreach ($dbh->query($sql) as $row)
print $row['employee_name'] .' - '. $row['employee_age'] ;
catch(PDOException $e)
echo $e->getMessage();

Questions 100: What is PHP's mysqli Extension?
Answers 100: The mysqli extension, or as it is sometimes known, the MySQL improved
extension, was developed to take advantage of new features found in MySQL
systems versions 4.1.3 and newer. The mysqli extension is included with PHP
versions 5 and later.
The mysqli extension has a number of benefits, the key enhancements over the
mysql extension being:
=>Object-oriented interface
=>Support for Prepared Statements
=>Support for Multiple Statements
=>Support for Transactions
=>Enhanced debugging capabilities
=>Embedded server support

1 comment:

  1. Looking great article and very informative one it’s very useful for us. Thank you!
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