PHP Guru: June 2013

Monday, 24 June 2013

PHP GET & POST :

PHP GET

PHP’s $_GET variable is used to collect names and data from a form using the method GET. This variable is an array of variable names and their values that are sent by HTTP GET method. It basic purpose is to collect data from a form. When the $_GET variable is used, all variables used are displayed in the URL and hence it should not be used for collecting secured information like passwords. The variables have a limited length.

Example:

On clicking submit the URL resembles to :
http://www.mysamplesite.com/sample.php?name=jim&age=37
The sample.php file can be used for catching the form data using $_GET
Hello <?php echo $_GET["name"]; ?>.<br />
You are <?php echo $_GET["age"]; ?> years old!

PHP POST

PHP’s $_POST variable is used to collect names and data from a form using the method POST. This variable is an array of variable names and their values that are sent by HTTP POST method. It basic purpose is to collect data from a form. When the $_ POST variable is used, all variables used are NOT displayed in the URL . Also, they have no restrictions to the length of the variables.

Example:

On clicking submit the URL resembles to:
http://www.mysamplesite.com/sample.php
The sample.php file can be used for catching the form data using $_POST
Hello <?php echo $_POST["name"]; ?>.<br />
You are <?php echo $_POST["age"]; ?> years old!

Explain when to use GET or POST. Provide example for both the ways.

Both GET and POST are used to collect data from a form. However, when security is desired $_POST should be used. When the $_ POST variable is used, all variables used are NOT displayed in the URL. Also, they have no restrictions to the length of the variables. GET should be used when the interaction with the form is more like a question. For e.g. firing a query etc. POST should be used more often when the interaction is more like an order or the interaction changes the state of the resource.

POST example:

On clicking submit the URL resembles to: http://www.mysamplesite.com/sample.php
The sample.php file can be used for catching the form data using $_POST
Hello <?php echo $_POST["name"]; ?>.<br />
You are <?php echo $_POST["age"]; ?> years old!

GET EXAMPLE

On clicking submit the URL resembles to : http://www.mysamplesite.com/sample.php?name=jim&age=37
The sample.php file can be used for catching the form data using $_GET
Hello <?php echo $_GET["name"]; ?>.<br />
You are <?php echo $_GET["age"]; ?> years old!

Sunday, 23 June 2013

Advantages of PHP:

PHP advantages

PHP offers a lot of security mechanisms,
Its easy connectivity abilities make it a popular choice of modular programming.
It can easily be interfaced with a variety of libraries, xml’s.
Its an open source software.
Syntax is similar to C and C++ and hence easy to remember the syntax.
Easy to use for creating dynamic web pages.
PHP has its own community where people can make their own scripts and post as per the requirement.

Advantage of php over Java

PHP is a simpler language specially designed for web applications
PHP is open source and hence customization becomes convenient.
PHP natively integrates with a large array of database engines, both open-source (MySQL, PostgreSQL, SQLite) and commercial (Oracle, MS SQL Server); while Java relies on JDBC drivers for database connectivity.

Some PHP interview questions:

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?

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.

Who is the father of php and explain the changes in php versions?

Rasmus Lerdorf for version changes go to http://php.net/ Marco Tabini is the founder and publisher of php|architect.

How can we submit from 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.

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.

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.

What is the difference between $message and $$message?

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 are the differences between require and include, include_once?

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 are the different tables present in mysql?

Total 5 types of tables we can create

1. MyISAM

2. Heap

3. Merge

4. InnoDB

5. ISAM

6. BDB

MyISAM is the default storage engine as of MySQL 3.23.

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.

What is meant by nl2br()?

Nl2br Inserts HTML line breaks before all newlines in a string string nl2br (string); For example: echo nl2br("god bless
you") will output "god bless
you" to your browser.

What are the current versions of apache, php, and mysql?

PHP: php 5.3
MySQL: MySQL 5.5
Apache: Apache 2.2

What are the reasons for selecting lamp (Linux, apache, mysql, php) instead of combination of other software programs, servers and operating systems?

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.

How can we encrypt and decrypt a data present in a mysql table using mysql?

AES_ENCRYPT () and AES_DECRYPT ()

How can we encrypt the username and password using php?

You can encrypt a password with the following Mysql>SET PASSWORD=PASSWORD("Password");
We can encode data using base64_encode($string) and can decode using base64_decode($string);

What are the different types of errors in php?

E_ERROR: A fatal error that causes script termination

E_WARNING: Run-time warning that does not cause script termination

E_PARSE: Compile time parse error.

E_NOTICE: Run time notice caused due to error in code

E_CORE_ERROR: Fatal errors that occur during PHP's initial startup (installation)

E_CORE_WARNING: Warnings that occur during PHP's initial startup

E_COMPILE_ERROR: Fatal compile-time errors indication problem with script.

E_USER_ERROR: User-generated error message.

E_USER_WARNING: User-generated warning message.

E_USER_NOTICE: User-generated notice message.

.E_STRICT: Run-time notices.

E_RECOVERABLE_ERROR: Catchable fatal error indicating a dangerous error

E_ALL: Catches all errors and warnings

What is the functionality of the function htmlentities?

Answer: htmlentities Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, except with htmlentities(), all characters which have HTML character entity equivalents are translated into these entities.

What is meant by urlencode and urldocode?

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.

What is the difference between the functions unlink and unset?

Unlink() deletes the given file from the file system.
unset() makes a variable undefined.

How can we register the variables into a session?

We can use the session_register ($ur_session_var) function.

How can we get the properties (size, type, width, height) of an image using php image functions?

To know the Image type use exif_imagetype () function
To know the Image size use getimagesize () function
To know the image width use imagesx () function
To know the image height use imagesy() function

What is the maximum size of a file that can be uploaded using php and how can we change this?

You can change maximum size of a file set upload_max_filesize variable in php.ini file.

How can we increase the execution time of a php script?

Set max_execution_time variable in php.ini file to your desired time in second.

How can we take a backup of a mysql table and how can we restore it.?

Create a full backup of your database: shell> mysqldump tab=/path/to/some/diropt db_name Or: shell> mysqlhotcopy db_name /path/to/some/dir
The full backup file is just a set of SQL statements, so restoring it is very easy:

shell> mysql "."Executed";
mysql_close($link2);

How many ways can we get the value of current session id?

session_id() function returns the session id for the current session.

How can we destroy the session, how can we unset the variable of a session?

session_destroy and session_unset

How can we destroy the cookie?

Set same the cookie in past

What is the difference between ereg_replace() and eregi_replace()?

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.

How can we know the count/number of elements of an array?

2 ways
a) sizeof($urarray) This function is an alias of count()
b) count($urarray)
interestingly if u just pass a simple var instead of a an array it will return 1.

What is the maximum length of a table name, database name, and fieldname in mysql?

Database name- 64
Table name -64
Fieldname-64

How many values can the SET function of mysql takes?

Mysql set can take zero or more values but at the maximum it can take 64 values

What is maximum size of a database in mysql?

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 â€" 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 Limit
Linux 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

What is meant by MIME?

Multipurpose Internet Mail Extensions.
WWW ability to recognise 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.

What is meant by PEAR in php?

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.

http://pear.php.net/manual/en/about.pear.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, a numeric array, or both.
mysql_fetch_object ( resource result )
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 PHP?

PHP Version 3.0 is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly.

What is the difference between include and require?

If you require a file and it cannot be found, the script will terminate with a fatal error. If you use include then you will get an error but the script will continue to execute. Therefore when the information you wish to reference from another file is essential to the correct running of a page, use require.

Is PHP a case sensitive programming language?

PHP is a partially case sensitive programming language. We can use function names, class names in case insensitive manner.

What is mean by LAMP?

LAMP means combination of Linux, Apache, MySQL and PHP.

How do you get the user's ip address in PHP?

Using the server variable: $_SERVER['REMOTE_ADDR']

How to find the number of elements in an array?

Using count($array) or sizeof($array).

How do you make one way encryption for your passwords in PHP?

Using md5 function or sha1 function

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 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 echo and print statement?

Echo() can take multiple expressions,Print cannot take multiple expressions.

Print return true or false based on success or failure whereas echo just does what its told without letting you know whether or not it worked properly.

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.

Session stored in server.

Explain about PHP looping?

Looping statements are used in PHP to execute the code for a developer defined number of times. PHP has these following looping statements they are while, do while, for and for each. Foreach is used to loop a block of code in each element in an array.

What is triggers ? Does MySQL supports it ?

A trigger is a database object which is associated with particular database table. Triggers gets called automatically when particular event(INSERT, UPDATE, DELETE) occurs on table.
In MySQL, Triggers gets supported after MySQL 5.0.2

What is difference between mysql_connect and mysql_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.

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 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 are the features and advantages of OBJECT ORIENTED PROGRAMMING?

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.

Three basic types of runtime errors in PHP:

1. Notices: These are small, 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 the default behavior can be changed.

2. Warnings: Warnings are more severe errors like 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.

Different types of errors in php:

E_ERROR: A fatal error that causes script termination

E_WARNING: Run-time warning that does not cause script termination

E_PARSE: Compile time parse error.

E_NOTICE: Run time notice caused due to error in code

E_CORE_ERROR: Fatal errors that occur during PHP's initial startup (installation)

E_CORE_WARNING: Warnings that occur during PHP's initial startup

E_COMPILE_ERROR: Fatal compile-time errors indication problem with script.

E_USER_ERROR: User-generated error message.

E_USER_WARNING: User-generated warning message.

E_USER_NOTICE: User-generated notice message.

.E_STRICT: Run-time notices.

E_RECOVERABLE_ERROR: Catchable fatal error indicating a dangerous error

E_ALL: Catches all errors and warnings

Monday, 17 June 2013

E-mail Validation

The function below checks if the content has the general syntax of an email.

This means that the input data must contain an @ sign and at least one dot (.). Also, the @ must not be the first character of the email address, and the last dot must be present after the @ sign, and minimum 2 characters before the end:

function validateForm()
{
var x=document.forms["myForm"]["email"].value;
var atpos=x.indexOf("@");
var dotpos=x.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length)
{
alert("Not a valid e-mail address");
return false;
}
}

<form name="myForm" action="demo_form.asp" onsubmit="return validateForm();" method="post">
Email: <input type="text" name="email">
<input type="submit" value="Submit">
</form>

JavaScript Form Validation

JavaScript can be used to validate data in HTML forms before sending off the content to a server.

Form data that typically are checked by a JavaScript could be:

has the user left required fields empty?
has the user entered a valid e-mail address?
has the user entered a valid date?
has the user entered text in a numeric field?

Required Fields

The function below checks if a field has been left empty. If the field is blank, an alert box alerts a message, the function returns false, and the form will not be submitted:

function validateForm()
{
var x=document.forms["myForm"]["fname"].value;
if (x==null || x=="")
{
alert("First name must be filled out");
return false;
}
}

The function above could be called when a form is submitted:

<form name="myForm" action="demo_form.asp" onsubmit="return validateForm()" method="post">
First name: <input type="text" name="fname">
<input type="submit" value="Submit">
</form>

Saturday, 1 June 2013

Youth movement for Developed India 2020

Recently, in Hyderabad, I met a group of citizens who are putting into practice the motto of transforming of our youth into enlightened citizen. The Lead India 2020 Foundation created by Dr. N.B. Sudershan at Hyderabad is training thousands of students in many districts of Andhra Pradesh in partnership with the District Administration. Particularly, I happened to know the transformation which has taken place among the students of Medak district. As per the district authorities the impact of the training on the students is visible in terms of self-discipline, love for their parents and teachers shedding of stage fear and recognition of their duties towards the nation. I talked to Ms. Padma, a student leader from Andhra Pradesh Tribal Welfare School, Nalgonda who related how she weaned her father away from smoking after imbibing the spirit of the 10 point oath from the Lead India Training Camp. This gives me an assurance that the youth of our country are on the right path through this mission oriented programme. With the ignited minds of the 540 million youth below the age of 25, which I consider is the most powerful resource on the earth, under the earth and above the earth, we have to empower the youth through value based education and leadership

By, Dr. APJ Abdulkalam

Vision 2020 Missions

Air transportation is a vital component of the communication network which helps to transport people on business, government officials, leisure travelers, transport of perishable and other goods. The networking helps to establish production centers in the interiors where there is advantage of low cost labor, low raw materials cost and low infrastructural cost. The air transportation while helping growth of interior regions, also helps industry, business sector to produce products at lower costs enabling competitiveness in the global market. The aircraft chosen for operation along with the airport infrastructure provided must be able to provide low cost solutions for transportation of men and materials. It would mean that there is a need for an aircraft whose acquisition and operating costs are low and also it should be capable of being operated from airports with minimal infrastructure and instrumentation facility. It may be pertinent to point out that the infrastructure cost for providing air connectivity between city pairs is lower than that for either road or rail connectivity. Is it a dream or is it possible?



There is a need for new generation of turboprop and turbojet aircraft that are cheaper to acquire and costs less to operate and are independent of costly airport infrastructure and instrumentation. Safe, nearly all weather access to any location in the country with an existing landing facility is a critical need for all round growth. With this goal in mind, I would recommend NAL to become the nodal agency to work on a 70 seater aircraft which should be so designed that with only change in fuselage length should be able to vary the passenger capacity to 50 or 90. With the technology available in the space programme, missile programme, LCA programme and other aircraft programme in the country, definitely realization of design, development and leading to production of 70 seater passenger aircraft before 2020 is possible.


Missions
Missions for enabling timely availability of a cost effective state of the art aircraft in service before 2020 are 1. System design: Modular system design leading cost effective variants of passenger aircraft of different capacities. Objective should be to reduce acquisition cost by 25%, operation cost by 25%, maintenance cost by 50% and emission reduced by 70%. 2. Avionics: Design and development of integrated avionics with COTS technology and open system architecture. 3. Power Plant: Next generation modular power plant for varying thrust condition. 4. Structures: Composite airframe, NLF adoptive wing including structural health monitoring system. Self clean, De-icing and abrasive resistant coating system. 5. Control system: Fly by wire flight control system. Aim for all electric architecture. 6. Maintenance: Advanced maintenance systems using IVHM, SHM and faster trouble. 7. Integrated Health monitoring: Development of integrated monitoring system for all utility system over the entire fleet for enhancing reliability and reduce maintenance cost. 8. Simulator and flight testing: Development of state of the art simulator which will reduce the over all time required for training of the pilots and also reduce the number of hours of flight tests needed for certification for induction into operation.

By, Dr. APJ Abdulkalam