PHP Interview Questions and Answers for Experienced basic advanced 2015-2016

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Question: What type of inheritance supports by PHP?

There are following type of inheritance
Single Inheritance - Support by PHP
Multiple Inheritance - Not support
Hierarchical Inheritance - Support by PHP
Multilevel Inheritance - Support by PHP


Question: How do you call a constructor for a parent class?

parent::constructor($value);


Question: What is the use of header() function in php?

1. Header is used to redirect from current page to another:
header("Location: newpage.php");

2. Header is used to send HTTP status code.
header("HTTP/1.0 404 Not Found");

3. Header is used to send Send a raw HTTP header
header('Content-Type: application/pdf');


Question: What are default session time and path?

Session Time: 1440 seconds
Session Path: /tmp folder in server


Question: What is the difference between the functions unlink and unset?

unlink: It is used to remove the file from server.
unlink('/path/file.phtml');

unset: It is used to remove the variable.
unset($variableName);

Question: What is MIME?

The Full form of MIME is "Multi-purpose Internet Mail Extensions".

It is extension of e-mail protocol helps to exchanges the different kids of data files over the internet.
Data files may be audio, video, images, application programs and ASCII etc.


Question: What do you mean by PEAR?

PHP Extension and Application Repository (PEAR) is a framework and repository for reusable PHP components.

Question: How to upload the file using CURL?

You can upload a file using CURL.

See following points.
1. Uploading file size must be less than allowed file by Server.
2. If file size is heady, May take more time.
3. replace "uploadFile.zip" with file which you want to upload WITH full path.
4. replace "http://localhost/test/index2" with URL where server has given functionality to upload file.

$file_name_with_full_path = realpath('uploadFile.zip');      
       $url = "http://localhost/test/index2";
       $post_data = array(
           "foo" => "bar",
           "upload" => "@".$file_name_with_full_path
       );
       try {
           $ch = curl_init();
           curl_setopt($ch, CURLOPT_URL, $url);
           curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
           curl_setopt($ch, CURLOPT_POST, 1);
           curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
           $output = curl_exec($ch);
           curl_close($ch);
       } catch (Exception $e) {
           echo $e->getMessage();
           die;
       }


Question: How can we get the current session id?
echo session_id();

You can also set the session_id using same above function.


Question: Can I set the header in CURL?

Yes, you can set the header in CURL using CURLOPT_HEADER.
curl_setopt($ch, CURLOPT_HTTPHEADER, Array("Content-Type: text/xml"));



Question: How can i execute PHP File using Command Line?

For this, you need PHP CLI(Commnd line interface)
Just login to you command line interface.
You have to prepend the "PHP" and need to mention the full-path/relative of file
Execute the file in following way.
php E://wamp/www/project/myfile.php


Question: What are different type of sorting functions in PHP?

sort() - sort arrays in ascending order. asort() - sort associative arrays in ascending order, according to the value.
ksort() - sort associative arrays in ascending order, according to the key.
krsort() - sort associative arrays in descending order, according to the key.
array_multisort() - sort the multi dimension array.
usort()- Sort the array using user defined function.
arsort() - sort associative arrays in descending order, according to the value.
rsort() - sort arrays in descending order.


Question: How to save the session data into database?

To maintain the session data, we can use session_set_save_handler function.
session_set_save_handler ( 'openFunction' , 'closeFunction', 'readFunction' , 'writeFunction' , 'destroyFunction', 'gcFunction' )

In this function, we provide 6 callback functions which call automatically.

For Example

openFunction will be called automatically when session start.
writeFunction will be called automatically when you write in the session.
destroyFunction will be called automatically when you destroy in the session.
gcFunction will be called automatically when session inactive for long time.
closeFunction will be called automatically when session end.
readFunction will be called automatically when you read the session.

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PHP Interview Questions and Answers 2015

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What is PHP?

Ans:PHP is a server side scripting language commonly used for web applications. PHP has many frameworks and cms for creating websites.Even a non technical person can cretae sites using its CMS.WordPress,osCommerce are the famus CMS of php.It is also an object oriented programming language like java,C-sharp etc.It is very eazy for learning

What is the use of "echo" in php?

Ans:It is used to print a data in the webpage, Example: <?php echo 'Car insurance'; ?> , The following code print the text in the webpage

How to include a file to a php page?

Ans:We can include a file using "include() " or "require()" function with file path as its parameter.

What's the difference between include and require?

Ans:If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.

require_once(), require(), include().What is difference between them?
require() includes and evaluates a specific file, while require_once() does that only if it has not been included before (on the same page). So, require_once() is recommended to use when you want to include a file where you have a lot of functions for example. This way you make sure you don't include the file more times and you will not get the "function re-declared" error.

Differences between GET and POST methods ?

Ans:We can send 1024 bytes using GET method but POST method can transfer large amount of data and POST is the secure method than GET method .

How to declare an array in php?

Ans:Eg : var $arr = array('apple', 'grape', 'lemon');

What is the use of 'print' in php?

Ans:This is not actually a real function, It is a language construct. So you can use with out parentheses with its argument list.
Example print('PHP Interview questions');
print 'Job Interview ');

What is use of in_array() function in php ?

Ans:in_array used to checks if a value exists in an array

What is use of count() function in php ?

Ans:count() is used to count all elements in an array, or something in an object

What’s the difference between include and require?

Ans:It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.

What is the difference between Session and Cookie?

Ans:The main difference between sessions and cookies is that sessions are stored on the server, and cookies are stored on the user’s computers in the text file format. Cookies can not hold multiple variables,But Session can hold multiple variables.We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking

How to set cookies in PHP?

Ans:Setcookie("sample", "ram", time()+3600);

How to Retrieve a Cookie Value?

Ans:eg : echo $_COOKIE["user"];

How to create a session? How to set a value in session ? How to Remove data from a session?

Ans:Create session : session_start();
Set value into session : $_SESSION['USER_ID']=1;
Remove data from a session : unset($_SESSION['USER_ID'];

what types of loops exist in php?

Ans:for,while,do while and foreach (NB: You should learn its usage)

How to create a mysql connection?

Ans:mysql_connect(servername,username,password);

How to select a database?

Ans:mysql_select_db($db_name);

How to execute an sql query? How to fetch its result ?

Ans:$my_qry = mysql_query("SELECT * FROM `users` WHERE `u_id`='1'; ");
$result = mysql_fetch_array($my_qry);
echo $result['First_name'];

Write a program using while loop

Ans:$my_qry = mysql_query("SELECT * FROM `users` WHERE `u_id`='1'; ");
while($result = mysql_fetch_array($my_qry))
{
echo $result['First_name'.]."<br/>";
}

How we can retrieve the data in the result set of MySQL using PHP?

Ans:1. mysql_fetch_row
2. mysql_fetch_array
3. mysql_fetch_object
4. mysql_fetch_assoc

What is the use of explode() function ?

Ans:Syntax : array explode ( string $delimiter , string $string [, int $limit ] );
This function breaks a string into an array. Each of the array elements is a substring of string formed by splitting it on boundaries formed by the string delimiter.

What is the difference between explode() and split() functions?

Ans:Split function splits string into array by regular expression. Explode splits a string into array by string.

What is the use of mysql_real_escape_string() function?

Ans:It is used to escapes special characters in a string for use in an SQL statement

Write down the code for save an uploaded file in php.

Ans:if ($_FILES["file"]["error"] == 0)
{
move_uploaded_file($_FILES["file"]["tmp_name"],
      "upload/" . $_FILES["file"]["name"]);
      echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
}

How to create a text file in php?

Ans:$filename = "/home/user/guest/newfile.txt";
$file = fopen( $filename, "w" );
if( $file == false )
{
echo ( "Error in opening new file" ); exit();
}
fwrite( $file, "This is a simple test\n" );
fclose( $file );

How to strip whitespace (or other characters) from the beginning and end of a string ?

Ans:The trim() function removes whitespaces or other predefined characters from both sides of a string.

What is the use of header() function in php ?

Ans:The header() function sends a raw HTTP header to a client browser.Remember that this function must be called before sending the actual out put.For example, You do not print any HTML element before using this function.

How to redirect a page in php?

Ans:The following code can be used for it, header("Location:index.php");

How stop the execution of a php scrip ?

Ans:exit() function is used to stop the execution of a page

How to set a page as a home page in a php based site ?

Ans:index.php is the default name of the home page in php based sites

How to find the length of a string?

Ans:strlen() function used to find the length of a string

what is the use of rand() in php?

Ans:It is used to generate random numbers.If called without the arguments it returns a pseudo-random integer between 0 and getrandmax(). If you want a random number between 6 and 12 (inclusive), for example, use rand(6, 12).This function does not generate cryptographically safe values, and should not be used for cryptographic uses. If you want a cryptographically secure value, consider using openssl_random_pseudo_bytes() instead.

what is the use of isset() in php?

Ans:This function is used to determine if a variable is set and is not NULL

What is the difference between mysql_fetch_array() and mysql_fetch_assoc() ?

Ans:mysql_fetch_assoc function Fetch a result row as an associative array, While mysql_fetch_array() fetches an associative array, a numeric array, or both

What is mean by an associative array?

Ans:Associative arrays are arrays that use string keys is called associative arrays.

What is the importance of "method" attribute in a html form?

Ans:"method" attribute determines how to send the form-data into the server.There are two methods, get and post. The default method is get.This sends the form information by appending it on the URL.Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

What is the importance of "action" attribute in a html form?

Ans:The action attribute determines where to send the form-data in the form submission.

What is the use of "enctype" attribute in a html form?

Ans:The enctype attribute determines how the form-data should be encoded when submitting it to the server. We need to set enctype as "multipart/form-data" when we are using a form for uploading files

How to create an array of a group of items inside an HTML form ?

Ans:We can create input fields with same name for "name" attribute with squire bracket at the end of the name of the name attribute, It passes data as an array to PHP.
For instance :

<input name="MyArray[]" />  <input name="MyArray[]" />  <input name="MyArray[]" />  <input name="MyArray[]" />

Define Object-Oriented Methodology

Ans:Object orientation is a software/Web development methodology that is based on the modeling a real world system.An object is the core concept involved in the object orientation. An object is the copy of the real world enity.An object oriented model is a collection of objects and its inter-relationships

How do you define a constant?

Ans:Using define() directive, like define ("MYCONSTANT",150)

How send email using php?

Ans:To send email using PHP, you use the mail() function.This mail() function accepts 5 parameters as follows (the last 2 are optional). You need webserver, you can't send email from localhost. eg : mail($to,$subject,$message,$headers);

How to find current date and time?

Ans:The date() function provides you with a means of retrieving the current date and time, applying the format integer parameters indicated in your script to the timestamp provided or the current local time if no timestamp is given. In simplified terms, passing a time parameter is optional - if you don't, the current timestamp will be used.

Difference between mysql_connect and mysql_pconnect?

Ans:There is a good page in the php manual on the subject, in short mysql_pconnect() makes a persistent connection to the database which means a SQL link that do not close when the execution of your script ends. mysql_connect()provides only for the databasenewconnection while using mysql_pconnect , the function would first try to find a (persistent) link that's already open with the same host, username and password. If one is found, an identifier for it will be returned instead of opening a new connection... the connection to the SQL server will not be closed when the execution of the script ends. Instead, the link will remain open for future use.

What is the use of "ksort" in php?

Ans:It is used for sort an array by key in reverse order.

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

Ans:They are both variables. But $var is a variable with a fixed name. $$var is a variable who's name is stored in $var. For example, if $var contains "message", $$var is the same as $message.

What are the encryption techniques in PHP

Ans:MD5 PHP implements the MD5 hash algorithm using the md5 function,
eg : $encrypted_text = md5 ($msg);

mcrypt_encrypt :- string mcrypt_encrypt ( string $cipher , string $key , string $data , string $mode [, string $iv ] );
Encrypts plaintext with given parameters

What is the use of the function htmlentities?

Ans: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.

How to delete a file from the system

Ans:Unlink() deletes the given file from the file system.

How to get the value of current session id?

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

What are the differences between mysql_fetch_array(), mysql_fetch_object(), mysql_fetch_row()?

Ans: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 are the different types of errors in PHP ?

Ans: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.

what is sql injection ?

Ans:SQL injection is a malicious code injection technique.It exploiting SQL vulnerabilities in Web applications

What is x+ mode in fopen() used for?

Ans:Read/Write. Creates a new file. Returns FALSE and an error if file already exists

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