11.)
What
is difference between session and cookie?
Cookies
- stored on
CLIENT machine
- amount of
data to be stored is LIMITED
- it can only
store STRINGS
- quite
FASTER than a session
Session
- stored on
SERVER machine
- amount of
data to be stored is NOT LIMITED
- it can
store OBJECTS
- quite
SLOWER as compared to cookies
2) Difference
between implode and explode function?
The implode()
function takes an already existing array as
it's
argument, and concatenates the contents of
each element
in the array into a string.
where as
explode() function performs reverse to implode()
function. It
splits the string into items by a
delimiter,
such as a dash, ampersand, space and places each
item into a
new array.
Another
Answer:- Implode() Function
The implode
function is used to "join elements of an array with a string".
The implode()
function returns a string from elements of an array. It takes an array of
strings and joins them together into one string using a delimiter (string to be
used between the pieces) of your choice.
The implode
function in PHP is easily remembered as "array
to string", which simply means that it takes an array and returns a
string. It rejoins any array elements and returns the resulting string, which
may be put in a variable.
Suppose you
have an array like this $arr = Array
("A","E","I","O","U");
and you wish to combine it into a string, by putting the separator '-' between each element of the array.
How to do that?
$str = implode("-",$arr);
So your resulting string variable $str will be contain:
A-E-I-O-U
Syntax
and you wish to combine it into a string, by putting the separator '-' between each element of the array.
How to do that?
$str = implode("-",$arr);
So your resulting string variable $str will be contain:
A-E-I-O-U
Syntax
implode
(separator , array)
Example1
<html>
<body bgcolor="pink">
<h3>Implode Function</h3>
<?php
$arr=array ('I','am','simple','boy!');
echo implode(" ",$arr);
?>
</body>
</html>
<html>
<body bgcolor="pink">
<h3>Implode Function</h3>
<?php
$arr=array ('I','am','simple','boy!');
echo implode(" ",$arr);
?>
</body>
</html>
Output
Explode() Function
The explode
function is used to "Split a string by a specified string into pieces i.e.
it breaks a string into an array".
The explode
function in PHP allows us to break a string into smaller text with each break
occurring at the same symbol. This symbol is known as the delimiter. Using the explode command we will create an array from a string. The explode()
function breaks a string into an array, but the implode function returns a
string from the elements of an array.
For example
you have a string
$str="A E I O U";
now you want to make each name as an element of an array and access it individually so what you do:
$arr = explode(",", $str);
means : we have made pieces of string $text based on separator ','
and put the resulting array in variable $arr
So I used print_r ($arr); and the results are the following:
Array(
[0] => A
[1] => E
[2] => I
[3] => O
[4] => U
)
which is equal to:
$arr = Array ("A","E","I","O","U");
Syntax
explode (separator,string,limit)
Example1
<html>
<body bgcolor="pink">
<h3>Explode Function</h3>
<?php
$str="I am simple boy!";
print_r(explode(" ",$str));
?>
</body>
</html>
$str="A E I O U";
now you want to make each name as an element of an array and access it individually so what you do:
$arr = explode(",", $str);
means : we have made pieces of string $text based on separator ','
and put the resulting array in variable $arr
So I used print_r ($arr); and the results are the following:
Array(
[0] => A
[1] => E
[2] => I
[3] => O
[4] => U
)
which is equal to:
$arr = Array ("A","E","I","O","U");
Syntax
explode (separator,string,limit)
Example1
<html>
<body bgcolor="pink">
<h3>Explode Function</h3>
<?php
$str="I am simple boy!";
print_r(explode(" ",$str));
?>
</body>
</html>
Output
3)difference
between Innodb and Myisam?
There is
foolowing Differences between MYISAM and InnoDB
ENGINE:-
1)MYISAM does
not support the foreign key constraint and
transaction
but InnoDB support it.
2)MYISAM is
faster then the InnoDB but in case of perforing
the count
operation it takes more time then the InnoDB.
3) MYISAM
occupies less memory sapce for tables rather than
InnoDB
tables.
4)difference
between unlink and unset?
unlink-deletes
the file
unset-unsets
the variable
5)string
function?
PHP String Functions
PHP: indicates the
earliest version of PHP that supports the function.
|
Function
|
Description
|
PHP
|
||
|
Returns a
string with backslashes in front of the specified characters
|
4
|
|||
|
Returns a string
with backslashes in front of predefined characters
|
3
|
|||
|
Converts a
string of ASCII characters to hexadecimal values
|
3
|
|||
|
Alias of
rtrim()
|
3
|
|||
|
Returns a
character from a specified ASCII value
|
3
|
|||
|
Splits a
string into a series of smaller parts
|
3
|
|||
|
Converts a
string from one Cyrillic character-set to another
|
3
|
|||
|
Decodes a
uuencoded string
|
5
|
|||
|
Encodes a
string using the uuencode algorithm
|
5
|
|||
|
Returns how
many times an ASCII character occurs within a string and returns the
information
|
4
|
|||
|
Calculates
a 32-bit CRC for a string
|
4
|
|||
|
One-way
string encryption (hashing)
|
3
|
|||
|
Outputs
strings
|
3
|
|||
6)array and
array function?
|
Function
|
Description
|
|
Creates an
array
|
|
|
Changes all
keys in an array to lowercase or uppercase
|
|
|
Splits an
array into chunks of arrays
|
|
|
Creates an
array by using the elements from one "keys" array and one
"values" array
|
|
|
Counts all
the values of an array
|
|
|
Compare
arrays, and returns the differences (compare values only)
|
|
|
Compare
arrays, and returns the differences (compare keys and values)
|
|
|
Compare
arrays, and returns the differences (compare keys only)
|
|
|
Compare
arrays, and returns the differences (compare keys and values, using a
user-defined key comparison function)
|
|
|
Compare
arrays, and returns the differences (compare keys only, using a user-defined
key comparison function)
|
Arrays
An
array in PHP is actually
an ordered map. A map is a type that associates values to keys.
This type is optimized for several different uses; it can be treated as an
array, list (vector), hash table (an implementation of a map), dictionary,
collection, stack, queue, and probably more. As array values can be other arrays, trees and
multidimensional arrays are also possible.
Explanation
of those data structures is beyond the scope of this manual, but at least one
example is provided for each of them. For more information, look towards the
considerable literature that exists about this broad topic.
Syntax
Specifying with array()
An
array can be created using
the array() language construct.
It takes any number of comma-separated key => value pairs as arguments.
array(
key => value,
key2 => value2,
key3 => value3,
...
)
7)difference
between echo and print?
Comparison chart
|
Echo (PHP)
|
Print (PHP)
|
|
|
Parameters:
|
echo can
take more than one parameter when used without parentheses. The syntax is
echo expression [, expression[, expression] ... ]. Note that echo
($arg1,$arg2) is invalid.
|
print only
takes one parameter.
|
|
Return
value:
|
echo does
not return any value
|
print always
returns 1 (integer)
|
|
Syntax:
|
void echo (
string $arg1 [, string $... ] )
|
int print (
string $arg )
|
|
What is
it?:
|
In PHP,
echo is not a function but a language construct.
|
In PHP,
print is not a really function but a language construct. However, it behaves
like a function in that it returns a value.
|
8)What is the
difference between == and === in PHP?
When
comparing values in PHP for equality you can use either the == operator or the
=== operator. What’s the difference between the 2? Well, it’s quite simple. The
== operator just checks to see if the left and right values are equal. But, the
=== operator (note the extra “=”) actually checks to see if the left and right
values are equal, and also checks to see if they are of the same variable type
(like whether they are both booleans, ints, etc.).
9)Diffrence
between GET and POST?
GET
-Get method is default method.In this data is send with URL Not in a secured manner.
-GET form contents are passed as part of the URL, as a QUERY STRING.
- GET method have not security because of data view in addressbar. For ex: we can not use this method for checking login
- We can bookmark link with this method
- Server can log all action
- because of server log, we can pass 255 char. as query String.
-Get method is default method.In this data is send with URL Not in a secured manner.
-GET form contents are passed as part of the URL, as a QUERY STRING.
- GET method have not security because of data view in addressbar. For ex: we can not use this method for checking login
- We can bookmark link with this method
- Server can log all action
- because of server log, we can pass 255 char. as query String.
POST
-POST form contents are passed to the script as an input file As a result, much more form data can be passed, since you can't run into the limit on the length of a URL or the length of a command line or command line argument on the server.
- POST method have security of data.
- We can not bookmark page link
- We can pass unlimited data by this method as query string In GET method.
-In POST method data is submitted as a part of http request
- data is not visible in the url
- It is more secure but slower as compared to GET.
-POST form contents are passed to the script as an input file As a result, much more form data can be passed, since you can't run into the limit on the length of a URL or the length of a command line or command line argument on the server.
- POST method have security of data.
- We can not bookmark page link
- We can pass unlimited data by this method as query string In GET method.
-In POST method data is submitted as a part of http request
- data is not visible in the url
- It is more secure but slower as compared to GET.
10)Difference
between include and require and require_once?
Get method is
default method In this data is send with URL
Not a secure
manner.
In Post
method data send in body portion
Another Question:-
In GET method
- data is
submitted as a part of url
- data is
visible to the user
- it is not
secure but fast and quick
In POST
method
- data is
submitted as a part of http request
- data is not
visible in the url
- it is more
secure but slower as compared to GET
11)Current
version of Apache, Php and Mysql.
PHP: PHP 5.1.2
MySQL: MySQL 5.1
Apache: Apache 2.1
MySQL: MySQL 5.1
Apache: Apache 2.1
12)Difference
types of error 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
The following is a list of the error codes returned by PHP.
E_ERROR: Fatal error. Terminates the script.
E_WARNING: Warning that does not end the script.
E_PARSE: There is an error in the parser.
E_NOTICE: Non-fatal error in the code.
E_CORE_ERROR: Fatal error in the PHP installation.
E_CORE_WARNING: Warnings resulting form an error in the PHP installation.
E_COMPILE_ERROR: Fatal error that occurs when script is compiled.
E_USER_ERROR: Error generated by programmer's code.
E_USER_WARNING: Warning generated by programmer's code.
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
The following is a list of the error codes returned by PHP.
E_ERROR: Fatal error. Terminates the script.
E_WARNING: Warning that does not end the script.
E_PARSE: There is an error in the parser.
E_NOTICE: Non-fatal error in the code.
E_CORE_ERROR: Fatal error in the PHP installation.
E_CORE_WARNING: Warnings resulting form an error in the PHP installation.
E_COMPILE_ERROR: Fatal error that occurs when script is compiled.
E_USER_ERROR: Error generated by programmer's code.
E_USER_WARNING: Warning generated by programmer's code.
13)orderby,
groupby and having in mysql
Groupby: It
is a way to sub-total your results,or perform
some other
'aggregate' functions on them.
Orderby: It
is a simply a way to sort your results. It
doesn't
affect what shows up in your result set,only what
order it is
displayed.
14)join in
mysql
INNER JOIN
DISPLAYS ONLY THE RECORDS WHICH ARE SATISFYING
THE JOINING
CONDITION,WHERE AS IN AN OUTER JOIN IT DISPLAYS
THE RECORDS
WHICH ARE SATISFYING THE CONDITION AND ALSO
WHICH ARE NOT
SATIFYING THE CONDITION ALSO.
FOR
EXAMPLE TAKE EMP AND DEPT TABLE.
INNER JOIN
QUERY:
SELECT
EMPNO,ENAME,SAL,DEPT.DEPTNO,DNAME,LOC FROM EMP INNER
JOIN DEPT ON(EMP.DEPTNO=DEPT.DEPTNO)
OUTER JOIN
QUERY:
SELECT
EMPNO,ENAME,SAL,DEPT.DEPTNO,DNAME,LOC FROM EMP RIGHT
OUTER JOIN
DEPT ON(EMP.DEPTNO=DEPT.DEPTNO).
IN INNER JOIN
IT DISPLAYS ONLY 10,20 & 30 DEPARTMENTS.
IN OUTER JOIN
IT DISPLAYS 10,20,30 AND 40 DEPARTMENTS.
TAKE DEFAULT
TABLES FOR EXECUTION
|
Inner join:
displays only matching record from 2 tables
Outer join:
Left outer
join display all the records from 1st table even
if dont
have matching record in 2nd table
rignt outer
join display all the record from the 2nd table
even if
there is not matching record in 1st table
|
15)Date and
time in mysql
MySQL Time -
Formats
There are
three different types of time data types in MySQL: TIME, DATETIME, and
TIMESTAMP. If you would like to learn more about DATETIME and TIMESTAMP, then
check out our MySQL Date section, as we've covered them there.
This lesson will just be covering the basics of using TIME.
MySQL Time -
TIME
First you
need to create a MySQL table with a TIME type. We have one already created if
you want to use it: timeplayground.sql.
The TIME data
type can be used to store actual times as well as the amount of time between
two points in time (like the time between now and the weekend) that may
sometimes be larger than 23 hours. H - Hour; M - Minute; S - Second.
Standard format:
HH:MM:SS
Extended hour format:
HHH:MM:SS
Time Range:
-838:59:50 to 838:59:59
When manually
entering a time into MySQL it is highly recommended that you use the exact
format show above. MySQL allows for many different ways to enter a time, but
they don't always behave as you would expect. Using the standard/extended
format we have shown above will help you avoid annoying problems.
Below we have
entered 3 manual times into MySQL. The first is done in the recommended format,
the second is a shorthand version of the first and the final example is outside
the allowed time range.
PHP &
MySQL Code:
<?php
//This
assumes you have already created the 'dateplayground' table
//Connect to
DB
$query_manual1
= "INSERT INTO timeplayground (dp_name, dp_time)
VALUES ('TIME: Manual Time',
'12:10:00')"; //perfectly done
$query_manual2
= "INSERT INTO timeplayground (dp_name, dp_time)
VALUES ('TIME: Manual Time',
'1210')"; // will this shorthand work?
$query_manual3
= "INSERT INTO timeplayground (dp_name, dp_time)
VALUES ('TIME: Manual Time',
'978:31:12')"; //how about this?
mysql_query($query_manual1)
or die(mysql_error());
mysql_query($query_manual2)
or die(mysql_error());
mysql_query($query_manual3)
or die(mysql_error());
?>
MySQL Time -
NOW()
To get the
current time, use MySQL's built in function NOW(). NOW() contains both the date
and time information, but MySQL is smart enough to just use the data needed for
TIME.
PHP &
MySQL Code:
<?php
$query_auto =
"INSERT INTO timeplayground (dp_name, dp_time)
VALUE ('TIME: Auto NOW()', NOW()
)";
mysql_query($query_auto)
or die(mysql_error());
?>
MySQL
timeplayground.sql Displayed
Below is a
small PHP script to spit out a rough version of our timeplayground.sql table.
PHP &
MySQL Code:
<?php
$query =
"SELECT * FROM timeplayground";
$result =
mysql_query($query) or die(mysql_error());
echo
"<table border='1'><tr>";
for($i = 0;
$i < mysql_num_fields($result); $i++){
echo
"<th>".mysql_field_name($result, $i)."</th>";
}
echo
"</tr>";
while($row =
mysql_fetch_array($result)){
echo "<tr>";
for($i = 0; $i <
mysql_num_fields($result); $i++){
echo
"<td>". $row[$i] ."</td>";
}
echo "</tr>";
}
echo
"</table>";
?>
Finished
timeplayground.sql Display:
|
dp_name
|
dp_time
|
|
TIME:
Manual Time
|
12:10:00
|
|
TIME:
Manual Time
|
00:12:10
|
|
TIME:
Manual Time
|
838:59:59
|
|
TIME: Auto
NOW()
|
14:30:36
|
Our first
manual time was handled just fine, but our second one did not. MySQL
interpreted 1210 as MM:SS instead of HH:MM as we assumed. This is why it's best
to use the formats we've described at the beginning.
The third
manual entry was changed from 978:31:12 to 838:59:59, so that it would be
within TIME's range.
16)subqueries
in mysql
A subquery
is, in essence, a SELECT
statement that is most often used as part of another SELECT statement, but could also be used
with an INSERT,
UPDATE, or DELETE and other statements. Subqueries are
used in order to achieve very complex searches and complex reports, as well as
for various optimizations. You can use a subquery in the FROM clause of a SELECT to allow you to have essentially any
number of GROUP BY
clauses to further and further refine your result.
17)Difference
between connect and pconnect?
mysql_connect
opens up a database connection every time a page is loaded. mysql_pconnect
opens up a connection, and keeps it open across multiple requests.
mysql_pconnect uses less resources, because it does not need to establish a database connection every time a page is loaded.
mysql_pconnect uses less resources, because it does not need to establish a database connection every time a page is loaded.
Answer:- In this article I discuss the two
MySQL built-in connection functions "mysql_Connect()" and
"mysql_Pconnect()" in PHP. Suppose you want to insert some data into
the emp detail table of your database in a PHP application. The first
thing that must be done is to create a connection for the table data for the
operations and that is done using mysql_connect(), because before you can
access data in a database, you must create a connection to the database and
after performing all the operations on the database, you should close the
connection using the mysql_close() function, but a Pconnection is already open
and available for use at any time; the mysql_pconnect() function will not be
closed and will persist for future use.
Syntax
|
Mysql_connect('localhost');
|
Example
<?php
//use for connection
{
$con= mysql_connect('localhost');
echo "$con";
}
?>
Syntax
|
Mysql_pconnect('localhost');
|
The
Pconnect function uses minimumal resourses because the mysql_pconnect()
function is already connected with your database connection; it does need to
have a connection established with the database every time the page is loaded,
for when you want to persistent a connection.
When you want a connection then you first find a persistent connection link that is already open with the same host, username and password. The persistent connection is make a max connection and connected max clients. This connection is a multi-credential connection.
When you want a connection then you first find a persistent connection link that is already open with the same host, username and password. The persistent connection is make a max connection and connected max clients. This connection is a multi-credential connection.
Example
<?php
//use for persistence connection
$conn = mysql_pconnect('localhost');
echo $conn;
?>
Output
18)insert,
update,delete command in mysql
Syntax
It is
possible to write the INSERT INTO statement in two forms.
The first
form doesn't specify the column names where the data will be inserted, only
their values:
INSERT INTO
table_name
VALUES (value1, value2, value3,...)
VALUES (value1, value2, value3,...)
The second
form specifies both the column names and the values to be inserted:
INSERT INTO
table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)
VALUES (value1, value2, value3,...)
Update Data
In a Database
The UPDATE
statement is used to update existing records in a table.
Syntax
UPDATE
table_name
SET column1=value, column2=value2,...
WHERE some_column=some_value
SET column1=value, column2=value2,...
WHERE some_column=some_value
Delete Data
In a Database
The DELETE
FROM statement is used to delete records from a database table.
Syntax
DELETE FROM
table_name
WHERE some_column = some_value
WHERE some_column = some_value
19)Unique
key, primary key and foreign key in mysql.
Primary key -
Primary key means main key
def:- A
primary key is one which uniquely identifies a row
of a table.
this key does not allow null values and also
does not
allow duplicate values. for ex,
empno
empname salary
1
firoz 35000
2
basha 34000
3
chintoo 40000
it will not
the values as follows:
1 firoz
35000
1 basha
34000
chintoo 35000
Unique key
- single and main key
A unique is one which uniquely
identifies a row
of a table,
but there is a difference like it will not
allow
duplicate values and it will any number of
allow
null
values(In oracle).
it allows
only a single null value(In sql server 2000)
Both will
function in a similar way but a slight difference
will be
there. So, decalaring it as a primary key is the
best one.
foreign key -
a foreign key is one which will refer to a
primary key
of another table
for ex,
emp_table dept_table
empno empname
salary deptno deptno deptname
In the above
relation, deptno is there in emp_table which
is a primary
key of dept_table. that means, deptno is
refering the
dept_table.
20)Mysql
function.
Table of
Contents
mysql_affected_rows — Get number of affected rows in
previous MySQL operation
mysql_client_encoding — Returns the name of the character
set
mysql_close — Close MySQL connection
mysql_connect — Open a connection to a MySQL Server
mysql_create_db — Create a MySQL database
mysql_data_seek — Move internal result pointer
mysql_db_name — Retrieves database name from the
call to mysql_list_dbs
mysql_db_query — Selects a database and executes a
query on it
mysql_drop_db — Drop (delete) a MySQL database
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