PHP Interview Questions
1. How can we set and destroy the cookie n php?
Answer : 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;
2. What is the difference between ereg_replace() and eregi_replace()?
Answer : 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 characters.
3. What are the different functions in sorting an array?
Answer : Sort(), arsort(),asort(), ksort(),natsort(), natcasesort(),rsort(), usort(),array_multisort(), and uksort().
4. How can we know the count/number of elements of an array?
Answer : 2 ways
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)
5. What is session_set_save_handler in PHP?
Answer: 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.
6. How can I know that a variable is a number or not using a JavaScript?
Answer : 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.
7. List out some tools through which we can draw E-R diagrams for mysql.
Answer : Case Studio
Smart Draw
8. How can I retrieve values from one database server and store them in other database server using PHP?
Answer : 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,
But you cannot execute new query in $db1, even if you
supply the link as because the link was overwritten by the new db.so 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);
9. List out the predefined classes in PHP?
Answer :Directory
stdClass
__PHP_Incomplete_Class
exception
php_user_filter
10. How can I make a script that can be bi-language (supports English, French)?
Answer :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.
11. What are the difference between abstract class and interface?
Answer : 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.
12. How can we send mail using JavaScript?
Answer : 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.
13. How can we repair a MySQL table?
Answer : The syntex for repairing a MySQL table is
REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended]
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.
14. What are the advantages of stored procedures, triggers, indexes?
Answer: 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.
15. What is the maximum length of a table name, database name, and fieldname in MySQL?
Answer : 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:
16. How many values can the SET function of MySQL take?
Answer : MySQL set can take zero or more values but at the maximum it can take 64 values
17. What are the other commands to know the structure of table using MySQL commands except explain command?
Answer :describe Table-Name;
18. How many tables will create when we create table, what are they?
Answer : The ‘.frm’ file stores the table definition.
The data file has a ‘.MYD’ (MYData) extension.
The index file has a ‘.MYI’ (MYIndex) extension.
19. What is the purpose of the following files having extensions
1) .frm
2) .myd
3) .myi?
What do these files contain?
Answer : 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.
20. What is maximum size of a database in MySQL?
Answer : 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 tablespace 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
1. How can we set and destroy the cookie n php?
Answer : 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;
2. What is the difference between ereg_replace() and eregi_replace()?
Answer : 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 characters.
3. What are the different functions in sorting an array?
Answer : Sort(), arsort(),asort(), ksort(),natsort(), natcasesort(),rsort(), usort(),array_multisort(), and uksort().
4. How can we know the count/number of elements of an array?
Answer : 2 ways
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)
5. What is session_set_save_handler in PHP?
Answer: 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.
6. How can I know that a variable is a number or not using a JavaScript?
Answer : 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.
7. List out some tools through which we can draw E-R diagrams for mysql.
Answer : Case Studio
Smart Draw
8. How can I retrieve values from one database server and store them in other database server using PHP?
Answer : 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,
But you cannot execute new query in $db1, even if you
supply the link as because the link was overwritten by the new db.so 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);
9. List out the predefined classes in PHP?
Answer :Directory
stdClass
__PHP_Incomplete_Class
exception
php_user_filter
10. How can I make a script that can be bi-language (supports English, French)?
Answer :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.
11. What are the difference between abstract class and interface?
Answer : 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.
12. How can we send mail using JavaScript?
Answer : 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.
13. How can we repair a MySQL table?
Answer : The syntex for repairing a MySQL table is
REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended]
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.
14. What are the advantages of stored procedures, triggers, indexes?
Answer: 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.
15. What is the maximum length of a table name, database name, and fieldname in MySQL?
Answer : 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:
16. How many values can the SET function of MySQL take?
Answer : MySQL set can take zero or more values but at the maximum it can take 64 values
17. What are the other commands to know the structure of table using MySQL commands except explain command?
Answer :describe Table-Name;
18. How many tables will create when we create table, what are they?
Answer : The ‘.frm’ file stores the table definition.
The data file has a ‘.MYD’ (MYData) extension.
The index file has a ‘.MYI’ (MYIndex) extension.
19. What is the purpose of the following files having extensions
1) .frm
2) .myd
3) .myi?
What do these files contain?
Answer : 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.
20. What is maximum size of a database in MySQL?
Answer : 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 tablespace 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
