PHP Interview Questions
What's PHP ?
The PHP Hypertext Preprocessor is a programming language that allows
web developers to create dynamic content that interacts with databases. PHP is
basically used for developing web based software applications.
What Is a Session?
A session is a logical object created by the PHP engine to allow you to preserve
data across subsequent HTTP requests.
There is only one session object available to your PHP scripts at any time. Data
saved to the session by a script can be retrieved by the same script or another
script when requested from the same visitor.
Sessions are commonly used to store temporary data to allow multiple PHP pages
to offer a complete functional transaction for the same visitor.
What is meant by PEAR in php?
Answer1:
PEAR is the next revolution in PHP. This repository is bringing higher level
programming to PHP. PEAR is a framework and distribution system for reusable PHP
components. It eases installation by bringing an automated wizard, and packing
the strength and experience of PHP users into a nicely organised OOP library.
PEAR also provides a command-line interface that can be used to automatically
install "packages"
Answer2:
PEAR is short for "PHP Extension and Application Repository" and is pronounced
just like the fruit. The purpose of PEAR is to provide:
A structured library of open-sourced code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP
The PHP Foundation Classes (PFC),
The PHP Extension Community Library (PECL),
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project with the PEAR Group as the governing body.
The project has been founded by Stig S. Bakken in 1999 and quite a lot of people
have joined the project since then.
How can we know the number of days between two given dates using PHP?
Simple arithmetic:
$date1 = date('Y-m-d');
$date2 = '2006-07-01';
$days = (strtotime() - strtotime()) / (60 * 60 * 24);
echo "Number of days since '2006-07-01': $days";
How can we repair a MySQL table?
The syntex for repairing a mysql table is:
REPAIR TABLE tablename
REPAIR TABLE tablename QUICK
REPAIR TABLE tablename EXTENDED
This command will repair the table specified.
If QUICK is given, MySQL will do a repair of only the index tree.
If EXTENDED is given, it will create index row by row.
What is the difference between $message and $$message?
Anwser 1:
$message is a simple variable whereas $$message is a reference variable.
Example:
$user = 'bob'
is equivalent to
$holder = 'user';
$$holder = 'bob';
Anwser 2:
They are both variables. But $message is a variable with a fixed name. $$message
is a variable who's name is stored in $message. For example, if $message
contains "var", $$message is the same as $var.
What Is a Persistent Cookie?
A persistent cookie is a cookie which is stored in a cookie file permanently on
the browser's computer. By default, cookies are created as temporary cookies
which stored only in the browser's memory. When the browser is closed, temporary
cookies will be erased. You should decide when to use temporary cookies and when
to use persistent cookies based on their differences:
*Temporary cookies can not be used for tracking long-term information.
*Persistent cookies can be used for tracking long-term information.
*Temporary cookies are safer because no programs other than the browser can
access them.
*Persistent cookies are less secure because users can open cookie files see the
cookie values.
What does a special set of tags <?= and ?> do in PHP?
The output is displayed directly to the browser.
How do you define a constant?
Via define() directive, like define ("MYCONSTANT", 100);
What are the differences between require and include, include_once?
Anwser 1:
require_once() and include_once() are both the functions to include and evaluate
the specified file only once. If the specified file is included previous to the
present call occurrence, it will not be done again.
But require() and include() will do it as many times they are asked to do.
Anwser 2:
The include_once() statement includes and evaluates the specified file during
the execution of the script. This is a behavior similar to the include()
statement, with the only difference being that if the code from a file has
already been included, it will not be included again. The major difference
between include() and require() is that in failure include() produces a warning
message whereas require() produces a fatal errors.
Anwser 3:
All three are used to an include file into the current page.
If the file is not present, require(), calls a fatal error, while in include()
does not.
The include_once() statement includes and evaluates the specified file during
the execution of the script. This is a behavior similar to the include()
statement, with the only difference being that if the code from a file has
already been included, it will not be included again. It des not call a fatal
error if file not exists. require_once() does the same as include_once(), but it
calls a fatal error if file not exists.
Anwser 4:
File will not be included more than once. If we want to include a file once only
and further calling of the file will be ignored then we have to use the PHP
function include_once(). This will prevent problems with function redefinitions,
variable value reassignments, etc.
What is meant by urlencode and urldecode?
Anwser 1:
urlencode() returns the URL encoded version of the given string. URL coding
converts special characters into % signs followed by two hex digits. For
example: urlencode("10.00%") will return "10%2E00%25". URL encoded strings are
safe to be used as part of URLs.
urldecode() returns the URL decoded version of the given string.
Anwser 2:
string urlencode(str) - Returns the URL encoded version of the input string.
String values to be used in URL query string need to be URL encoded. In the URL
encoded version:
Alphanumeric characters are maintained as is.
Space characters are converted to "+" characters.
Other non-alphanumeric characters are converted "%" followed by two hex digits
representing the converted character.
string urldecode(str) - Returns the original string of the input URL encoded
string.
For example:
$discount ="10.00%";
$url = "http://domain.com/submit.php?disc=".urlencode($discount);
echo $url;
You will get "http://domain.com/submit.php?disc=10%2E00%25".
How To Get the Uploaded File Information in the Receiving Script?
Once the Web server received the uploaded file, it will call the PHP script
specified in the form action attribute to process them. This receiving PHP
script can get the uploaded file information through the predefined array called
$_FILES. Uploaded file information is organized in $_FILES as a two-dimensional
array as:
$_FILES[$fieldName]['name'] - The Original file name on the browser system.
$_FILES[$fieldName]['type'] - The file type determined by the browser.
$_FILES[$fieldName]['size'] - The Number of bytes of the file content.
$_FILES[$fieldName]['tmp_name'] - The temporary filename of the file in which
the uploaded file was stored on the server.
$_FILES[$fieldName]['error'] - The error code associated with this file upload.
The $fieldName is the name used in the <INPUT TYPE=FILE, NAME=fieldName>.
What is the difference between mysql_fetch_object and
mysql_fetch_array?
MySQL fetch object will collect first single matching record where
mysql_fetch_array will collect all matching records from the table in an array
How can I execute a PHP script using command line?
Just run the PHP CLI (Command Line Interface) program and provide the PHP script
file name as the command line argument. For example, "php myScript.php",
assuming "php" is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may
not execute properly in command line environment.
I am trying to assign a variable the value of 0123, but it keeps
coming up with a different number, what's the problem?
PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar
PHP interview questions for more numeric problems.
Would I use print "$a dollars" or "{$a} dollars" to print out the
amount of dollars in this example?
In this example it wouldn't matter, since the variable is all by
itself, but if you were to print something like "{$a},000,000 mln dollars", then
you definitely need to use the braces.
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))?
Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM
MyISAM is the default storage engine as of MySQL 3.23. When you fire the above
create query MySQL will create a MyISAM table.
How To Create a Table?
If you want to create a table, you can run the CREATE TABLE statement as shown
in the following sample script:
<?php
include "mysql_connection.php";
$sql = "CREATE TABLE Tech_links ("
. " id INTEGER NOT NULL"
. ", url VARCHAR(80) NOT NULL"
. ", notes VARCHAR(1024)"
. ", counts INTEGER"
. ", time TIMESTAMP DEFAULT sysdate()"
. ")";
if (mysql_query($sql, $con)) {
print("Table Tech_links created.\n");
} else {
print("Table creation failed.\n");
}
mysql_close($con);
?>
Remember that mysql_query() returns TRUE/FALSE on CREATE statements. If you run
this script, you will get something like this:
Table Tech_links created.
How can we encrypt the username and password using PHP?
Answer1
You can encrypt a password with the following Mysql>SET
PASSWORD=PASSWORD("Password");
Answer2
You can use the MySQL PASSWORD() function to encrypt username and password. For
example,
INSERT into user (password, ...) VALUES (PASSWORD($password”)), ...);
How do you pass a variable by value?
Just like in C++, put an ampersand in front of it, like $a = &$b
What is the functionality of the functions STRSTR() and STRISTR()?
string strstr ( string haystack, string needle ) returns part of haystack string
from the first occurrence of needle to the end of haystack. This function is
case-sensitive.
stristr() is idential to strstr() except that it is case insensitive.
When are you supposed to use endif to end the conditional statement?
When the original if was followed by : and then the code block without braces.
How can we send mail using JavaScript?
No. There is no way to send emails directly using JavaScript.
But you can use JavaScript to execute a client side email program send the email
using the "mailto" code. Here is an example:
function myfunction(form)
{
tdata=document.myform.tbox1.value;
location="mailto:mailid@domain.com?subject=...";
return true;
}
What is the functionality of the function strstr and stristr?
strstr() returns part of a given string from the first occurrence of a given
substring to the end of the string. For example: strstr("user@example.com","@")
will return "@example.com".
stristr() is idential to strstr() except that it is case insensitive.
What is the difference between ereg_replace() and
eregi_replace()?
eregi_replace() function is identical to ereg_replace() except that
it ignores case distinction when matching alphabetic characters.
How do I find out the number of parameters passed into function9.
?
func_num_args() function returns the number of parameters passed in.
What is the purpose of the following files having extensions:
frm, myd, and myi? What these files contain?
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,
If the variable $a is equal to 5 and variable $b is equal to
character a, what's the value of $$b?
100, it's a reference to existing variable.
How To Protect Special Characters in Query String?
If you want to include special characters like spaces in the query string,
you need to protect them by applying the urlencode() translation function.
The script below shows how to use urlencode():
<?php
print("<html>");
print("<p>Please click the links below"
." to submit comments about TECHPreparation.com:</p>");
$comment = 'I want to say: "It\'s a good site! :->"';
$comment = urlencode($comment);
print("<p>"
."<a href=\"processing_forms.php?name=Guest&comment=$comment\">"
."It's an excellent site!</a></p>");
$comment = 'This visitor said: "It\'s an average site! :-("';
$comment = urlencode($comment);
print("<p>"
.'<a href="processing_forms.php?'.$comment.'">'
."It's an average site.</a></p>");
print("</html>");
?>
Are objects passed by value or by reference?
Everything is passed by value.
What are the differences between DROP a table and TRUNCATE a
table?
DROP TABLE table_name - This will delete the table and its data.
TRUNCATE TABLE table_name - This will delete the data of the table, but not
the table definition.
How do you call a constructor for a parent class?
parent::constructor($value)
WHAT ARE THE DIFFERENT TYPES OF ERRORS IN PHP?
Here are three basic types of runtime errors in PHP:
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 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.
Internally, these variations are represented by twelve different error types
What's the special meaning of __sleep and __wakeup?
__sleep returns the array of all the variables than need to be saved, while
__wakeup retrieves them.
How can we submit a form without a submit button?
If you don't want to use the Submit button to submit a form, you can use
normal hyper links to submit a form. But you need to use some JavaScript
code in the URL of the link. For example:
<a href="javascript: document.myform.submit();">Submit Me</a>
Why doesn't the following code print the newline properly? <?php $str
= ‘Hello, there.\nHow are you?\nThanks for visiting techpreparation'; print
$str; ?>
Because inside the single quotes the \n character is not interpreted as
newline, just as a sequence of two characters - \ and n.
Would you initialize your strings with single quotes or double
quotes?
Since the data inside the single-quoted string is not parsed for variable
substitution, it's always a better idea speed-wise to initialize a string with
single quotes, unless you specifically need variable substitution.
How can we extract string 'abc.com ' from a string
http://info@abc.com using regular expression of php?
We can use the preg_match() function with "/.*@(.*)$/" as
the regular expression pattern. For example:
preg_match("/.*@(.*)$/","http://info@abc.com",$data);
echo $data[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?
Anwser 1:
When we submit a form, which has the GET method it displays pair of name/value
used in the form at the address bar of the browser preceded by url. Post method
doesn't display these values.
Anwser 2:
When you want to send short or small data, not containing ASCII characters, then
you can use GET” Method. But for long data sending, say more then 100 character
you can use POST method.
Once most important difference is when you are sending the form with GET method.
You can see the output which you are sending in the address bar. Whereas if you
send the form with POST” method then user can not see that information.
Anwser 3:
What are "GET" and "POST"?
GET and POST are methods used to send data to the server: With the GET method,
the browser appends the data onto the URL. With the Post method, the data is
sent as "standard input."
Major Difference
In simple words, in POST method data is sent by standard input (nothing shown in
URL when posting while in GET method data is sent through query string.
Ex: Assume we are logging in with username and password.
GET: we are submitting a form to login.php, when we do submit or similar action,
values are sent through visible query string (notice ./login.php?username=...&password=...
as URL when executing the script login.php) and is retrieved by login.php by
$_GET['username'] and $_GET['password'].
POST: we are submitting a form to login.php, when we do submit or similar
action, values are sent through invisible standard input (notice ./login.php)
and is retrieved by login.php by $_POST['username'] and $_POST['password'].
POST is assumed more secure and we can send lot more data than that of GET
method is limited (they say Internet Explorer can take care of maximum 2083
character as a query string).
Anwser 4:
In the get method the data made available to the action page ( where data is
received ) by the URL so data can be seen in the address bar. Not advisable if
you are sending login info like password etc. In the post method the data will
be available as data blocks and not as query string in case of get method.
Anwser 5:
When we submit a form, which has the GET method it pass value in the form of
query string (set of name/value pair) and display along with URL. With GET we
can a small data submit from the form (a set of 255 character) whereas Post
method doesn't display value with URL. It passes value in the form of Object and
we can submit large data from the form.
Anwser 6:
On the server side, the main difference between GET and POST is where the
submitted is stored. The $_GET array stores data submitted by the GET method.
The $_POST array stores data submitted by the POST method.
On the browser side, the difference is that data submitted by the GET method
will be displayed in the browser's address field. Data submitted by the POST
method will not be displayed anywhere on the browser.
GET method is mostly used for submitting a small amount and less sensitive data.
POST method is mostly used for submitting a large amount or sensitive data.
What is the difference between the functions unlink and unset?
unlink() is a function for file system handling. It will simply delete the file
in context.
unset() is a function for variable management. It will make a variable
undefined.
How come the code works, but doesn't for two-dimensional array of
mine?
Any time you have an array with more than one dimension, complex parsing syntax
is required. print "Contents: {$arr[1][2]}" would've worked.
How can we register the variables into a session?
session_register($session_var);
$_SESSION['var'] = 'value';
What is the difference between characters \023 and \x23?
The first one is octal 23, the second is hex 23.
With a heredoc syntax, do I get variable substitution inside the
heredoc contents?
Yes.
How can we submit form without a submit button?
We can use a simple JavaScript code linked to an event trigger of any form
field. In the JavaScript code, we can call the document.form.submit() function
to submit the form. For example: <input type=button value="Save"
onClick="document.form.submit()">
How can we create a database using PHP and mysql?
We can create MySQL database with the use of mysql_create_db($databaseName) to
create a database.
How many ways we can retrieve the date in result set of mysql using
php?
As individual objects so single record or as a set or arrays.
Can we use include ("abc.php") two times in a php page "makeit.php"?
Yes.
For printing out strings, there are echo, print and printf. Explain
the differences.
echo is the most primitive of them, and just outputs the contents following the
construct to the screen. print is also a construct (so parentheses are optional
when calling it), but it returns TRUE on successful output and FALSE if it was
unable to print out the string. However, you can pass multiple parameters to
echo, like:
<?php echo 'Welcome ', 'to', ' ', 'techpreparations!'; ?>
and it will output the string "Welcome to techpreparations!" print does not take
multiple parameters. It is also generally argued that echo is faster, but
usually the speed advantage is negligible, and might not be there for future
versions of PHP. printf is a function, not a construct, and allows such
advantages as formatted output, but it's the slowest way to print out data out
of echo, print and printf.
I am writing an application in PHP that outputs a printable version
of driving directions. It contains some long sentences, and I am a neat freak,
and would like to make sure that no line exceeds 50 characters. How do I
accomplish that with PHP?
On large strings that need to be formatted according to some length
specifications, use wordwrap() or chunk_split().
What's the output of the ucwords function in this example?
$formatted = ucwords("TECHPREPARATIONS IS COLLECTION OF INTERVIEW QUESTIONS");
print $formatted;
What will be printed is TECHPREPARATIONS IS COLLECTION OF INTERVIEW QUESTIONS.
ucwords() makes every first letter of every word capital, but it does not
lower-case anything else. To avoid this, and get a properly formatted string,
it's worth using strtolower() first.
What's the difference between htmlentities() and htmlspecialchars()?
htmlspecialchars only takes care of <, >, single quote ‘, double quote " and
ampersand. htmlentities translates all occurrences of character sequences that
have different meaning in HTML.
How can we extract string "abc.com" from a string
"mailto:info@abc.com?subject=Feedback" using regular expression of PHP?
$text = "mailto:info@abc.com?subject=Feedback";
preg_match('|.*@([^?]*)|', $text, $output);
echo $output[1];
Note that the second index of $output, $output[1], gives the match, not the
first one, $output[0].
So if md5() generates the most secure hash, why would you ever use
the less secure crc32() and sha1()?
Crypto usage in PHP is simple, but that doesn't mean it's free. First off,
depending on the data that you're encrypting, you might have reasons to store a
32-bit value in the database instead of the 160-bit value to save on space.
Second, the more secure the crypto is, the longer is the computation time to
deliver the hash value. A high volume site might be significantly slowed down,
if frequent md5() generation is required.
How can we destroy the session, how can we unset the variable of a
session?
session_unregister() - Unregister a global variable from the current
session
session_unset() - Free all session variables
What are the different functions in sorting an array?
Sorting functions in PHP:
asort()
arsort()
ksort()
krsort()
uksort()
sort()
natsort()
rsort()
How can we know the count/number of elements of an array?
2 ways:
a) sizeof($array) - This function is an alias of count()
b) count($urarray) - This function returns the number of elements in an array.
Interestingly if you just pass a simple var instead of an array, count() will
return 1.
How many ways we can pass the variable through the navigation between
the pages?
At least 3 ways:
1. Put the variable into session in the first page, and get it back from session
in the next page.
2. Put the variable into cookie in the first page, and get it back from the
cookie in the next page.
3. Put the variable into a hidden form field, and get it back from the form in
the next page.
What is the maximum length of a table name, a database name, or a
field name in MySQL?
Database name: 64 characters
Table name: 64 characters
Column name: 64 characters
How many values can the SET function of MySQL take?
MySQL SET function can take zero or more values, but at the maximum it can take
64 values.
What are the other commands to know the structure of a table using
MySQL commands except EXPLAIN command?
DESCRIBE table_name;
How can we find the number of rows in a table using MySQL?
Use this for MySQL
SELECT COUNT(*) FROM table_name;
What's the difference between md5(), crc32() and sha1() crypto on
PHP?
The major difference is the length of the hash generated. CRC32 is, evidently,
32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit
value. This is important when avoiding collisions.
How can we find the number of rows in a result set using PHP?
Here is how can you find the number of rows in a result set in PHP:
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";
How many ways we can we find the current date using MySQL?
SELECT CURDATE();
SELECT CURRENT_DATE();
SELECT CURTIME();
SELECT CURRENT_TIME();
Give the syntax of GRANT commands?
The generic syntax for GRANT is as following
GRANT [rights] on [database] TO [username@hostname] IDENTIFIED BY [password]
Now rights can be:
a) ALL privilages
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all databse by usingh *.* or some specific database by
database.* or a specific table by database.table_name.
Give the syntax of REVOKE commands?
The generic syntax for revoke is as following
REVOKE [rights] on [database] FROM [username@hostname]
Now rights can be:
a) ALL privileges
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all database by using *.* or some specific database by
database.* or a specific table by database.table_name.
What is the difference between CHAR and VARCHAR data types?
CHAR is a fixed length data type. CHAR(n) will take n characters of storage even
if you enter less than n characters to that column. For example, "Hello!" will
be stored as "Hello! " in CHAR(10) column.
VARCHAR is a variable length data type. VARCHAR(n) will take only the required
storage for the actual number of characters entered to that column. For example,
"Hello!" will be stored as "Hello!" in VARCHAR(10) column.
How can we encrypt and decrypt a data present in a mysql table using
mysql?
AES_ENCRYPT() and AES_DECRYPT()
Will comparison of string "10" and integer 11 work in PHP?
Yes, internally PHP will cast everything to the integer type, so numbers 10 and
11 will be compared.
What is the functionality of MD5 function in PHP?
string md5(string)
It calculates the MD5 hash of a string. The hash is a 32-character hexadecimal
number.
How can I load data from a text file into a table?
The MySQL provides a LOAD DATA INFILE command. You can load data from a file.
Great tool but you need to make sure that:
a) Data must be delimited
b) Data fields must match table columns correctly
How can we know the number of days between two given dates using
MySQL?
Use DATEDIFF()
SELECT DATEDIFF(NOW(),'2006-07-01');
How can we change the name of a column of a table?
This will change the name of column:
ALTER TABLE table_name CHANGE old_colm_name new_colm_name
How can we change the data type of a column of a table?
This will change the data type of a column:
ALTER TABLE table_name CHANGE colm_name same_colm_name [new data type]
What is the difference between GROUP BY and ORDER BY in SQL?
To sort a result, use an ORDER BY clause.
The most general way to satisfy a GROUP BY clause is to scan the whole table and
create a new temporary table where all rows from each group are consecutive, and
then use this temporary table to discover groups and apply aggregate functions
(if any).
ORDER BY [col1],[col2],...[coln]; Tells DBMS according to what columns it should
sort the result. If two rows will have the same value in col1 it will try to
sort them according to col2 and so on.
GROUP BY [col1],[col2],...[coln]; Tells DBMS to group (aggregate) 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.
What is meant by MIME?
Answer 1:
MIME is Multipurpose Internet Mail Extensions is an Internet standard for the
format of e-mail. However browsers also uses MIME standard to transmit files.
MIME has a header which is added to a beginning of the data. When browser sees
such header it shows the data as it would be a file (for example image)
Some examples of MIME types:
audio/x-ms-wmp
image/png
application/x-shockwave-flash
Answer 2:
Multipurpose Internet Mail Extensions.
WWW's ability to recognize and handle files of different types is largely
dependent on the use of the MIME (Multipurpose Internet Mail Extensions)
standard. The standard provides for a system of registration of file types with
information about the applications needed to process them. This information is
incorporated into Web server and browser software, and enables the automatic
recognition and display of registered file types. …
How can we know that a session is started or not?
A session starts by session_start() function.
This session_start() is always declared in header portion. it always declares
first. then we write session_register().
What are the differences between mysql_fetch_array(),
mysql_fetch_object(), mysql_fetch_row()?
Answer 1:
mysql_fetch_array() -> Fetch a result row as a combination of associative array
and regular array.
mysql_fetch_object() -> Fetch a result row as an object.
mysql_fetch_row() -> Fetch a result set as a regular array().
Answer 2:
The difference between mysql_fetch_row() and mysql_fetch_array() is that the
first returns the results in a numeric array ($row[0], $row[1], etc.), while the
latter returns a the results an array containing both numeric and associative
keys ($row['name'], $row['email'], etc.). mysql_fetch_object() returns an object
($row->name, $row->email, etc.).
If we login more than one browser windows at the same time with same
user and after that we close one window, then is the session is exist to other
windows or not? And if yes then why? If no then why?
Session depends on browser. If browser is closed then session is lost. The
session data will be deleted after session time out. If connection is lost and
you recreate connection, then session will continue in the browser.
What are the MySQL database files stored in system ?
Data is stored in name.myd
Table structure is stored in name.frm
Index is stored in name.myi
What is the difference between PHP4 and PHP5?
PHP4 cannot support oops concepts and Zend engine 1 is used.
PHP5 supports oops concepts and Zend engine 2 is used.
Error supporting is increased in PHP5.
XML and SQLLite will is increased in PHP5.
Can we use include(abc.PHP) two times in a PHP page makeit.PHP”?
Yes we can include that many times we want, but here are some things to make
sure of:
(including abc.PHP, the file names are case-sensitive)
there shouldn't be any duplicate function names, means there should not be
functions or classes or variables with the same name in abc.PHP and makeit.php
What are the differences between mysql_fetch_array(),
mysql_fetch_object(), mysql_fetch_row()?
mysql_fetch_array - Fetch a result row as an associative array and a numeric
array.
mysql_fetch_object - Returns an object with properties that correspond to the
fetched row and moves the internal data pointer ahead. Returns an object with
properties that correspond to the fetched row, or FALSE if there are no more
rows
mysql_fetch_row() - Fetches one row of data from the result associated with the
specified result identifier. The row is returned as an array. Each result column
is stored in an array offset, starting at offset 0.
What is meant by nl2br()?
Anwser1:
nl2br() inserts a HTML tag <br> before all new line characters \n in a string.
echo nl2br("god bless \n you");
output:
god bless<br>
you
How can we encrypt and decrypt a data presented in a table using
MySQL?
You can use functions: AES_ENCRYPT() and AES_DECRYPT() like:
AES_ENCRYPT(str, key_str)
AES_DECRYPT(crypt_str, key_str)
How can I retrieve values from one database server and store them in
other database server using PHP?
For this purpose, you can first read the data from one server into session
variables. Then connect to other server and simply insert the data into the
database.
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