PHP Interview Questions II

How to call a C function within PHP?
We can call some of the C functions from PHP like printf() fputs() fwrite() fgetc() exit() and so many others but not all.

What is the purpose of ob_start() ?
This function will turn output buffering on. While output buffering is ON no output is sent from the script (but headers), instead the output is stored in an internal buffer. to get contents from output buffer we can use ob_get_contents function.

Where does the session stored, either client side or server side?
PHP Session is used to maintain client's previous state and it's stored onserver side

If we have a button on a simple page and a user clicks on the button, then how we can come to know how many times the user has clicked on the button?
Make a javascript function. Call that function each time the user click on the button.
In javascript take a global variable to count the click. eg

var count 0;
function count_click()
{
count++;
return count;
}

This function will return you each count of user click.

How do you upload videos using PHP?
By adding the file field to browse the file to upload .And you need to set the enctype of the form to "multipart-form-data" to get the $_FILES in the form submition. Once you get the $_FILES['tmp_name'] in the submition then you can move the file from this temporary location to your required location by php move_uploaded_file(tmp_location destination) function.
Whether Videos or Audios those are nothing but binary files. You may upload them using simple HTML forms (using enctype multipart/form-data) and may store they either in MySQL database BLOB type column (MySQL's binary data type storing column) or you may store they in any directory (filesystem) on the server.

why we need a function like fetch_object and what is the purpose of using it?
Fetch array normally retrives the records based on array index. i.e. like $row[1], but if you want to retrieve the record based on the column name we can use fetch_object i.e. $row['username']



What is PHP header()?
In commons, header() being used for page redirection, whereby a specific location being define. However header() can be use more than just that.

header() may also be use for page authentication, assigning content type, cache control, etc.

use of htaccess
.htaccess files are configuration files of Apache Server which provide a way to make configuration changes on a per-directory basis. A file, containing one or more configuration directives, is placed in a particular document directory, and the directives apply to that directory, and all subdirectories thereof.

How to get domain name?
Yes it is possible by $_server[HTTP_HOST]
eg:

will result the domain name.





How to prevent form hijacking in PHP?


Following things can be done for preventing your PHP Form from Hijacking

1. Make register_globals to off to prevent Form Injection with malicious data.
2. Make Error_reporting to E_ALL so that all variables will be intialized before using them.
3. Make practice of using htmlentities(), strip_tags(), utf8_decode() and addslashes() for filtering malicious data in php
4. Make practice of using mysql_escape_string() in mysql.

Few more coding practices can be done to avoid PP Form Hijacking

1. User Input Sanitization-Never trust web user submitted data. Follow good clieint side data validation practices with regular expressions before submitting data to the server.
2. Form Submision Key Validation: A singleton method can be used to generate a Session form key & validating form being submitted for the same value against hidden form key params.
3. SQL injection attacks by using mysql_escape_string()

What is the difference between session_register and $_session?

session_register() is used for register one or more global variables with the current session. While $_SESSION[] array is used for storing one or more variables with in the current session array. session_register() depends upon register_global is enable or disable If it disable it will not work.

What is CAPTCHA?

CAPTCHA stands for Completely Automated Public Turing Test to tell Computers and Humans Apart. To prevent spammers from using bots to automatically fill out forms CAPTCHA programmers will generate an image containing distorted images of a string of numbers and letters. Computers cannot determine what the numbers and letters are from the image but humans have great pattern recognition abilities and will be able to fairly accurately determine the string of numbers and letters. By entering the numbers and letters from the image in the validation field the application can be fairly assured that there is a human client using it.

How we know browser properties?

get_browser() attempts to determine the capabilities of the user's browser. This is done by looking up the browser's information in the browscap.ini file.

echo $_SERVER['HTTP_USER_AGENT'] .

---

\n ;

$browser get_browser();

foreach ($browser as $name > $value) {
echo $name $value
\n ;
}

What is diff between srand & shuffle?
srand function seeds the random number generator with given seed. Function shuffle is used for shuffling the array values. This function generates new keys for the array elements.

Mysql command to fetch onlythe unique values?
select distinct column_name from table_name;

how can a script come to a clear termination?
using exit 0; you may force to terminate clearly a PHP script with

What is random number?
A random number is a number generated by a process, whose outcome is unpredictable, and which cannot be subsequentially reliably reproduced.


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

Single quote strings are executed faster than double quotes
When we use single quote for string then php will not parse the things between that quote. It simply assign as it is.
But when we use double quotes then it will parse for variables and other things between double quotes.

What are magic quotes in PHP?
Some special characters in PHP like single quote( ' ) double quote( ) amperson ( & ) etc. are escape by slash its called magic quotes.


Describe the process from a users web browser, to the web-server and back again.

When user submits the form from the browser, the form is submitted to the Web server where it filters the server-side languages and client-side languages. Now the server side languages is parsed and executed on the server and queries if any to the backend i.e. database and gets values from there. After whole process or form is executed, the result is thrown to the web browser on the client side. And client side scripts like javascript and HTML are already parsed on the user's browser only.


How would you check that a string is a palindrome? *hint* using only one statement.
For checking tht the string is palindrome, just check the original string with its strrev() result, if both matches, than the string is palindrome.


What is 'htmlentities' and it's relationship with preventing XSS attacks/vulnerabilities?
XSS or crossite attacks is like when you change the URL and try to change the form submit for attacking to the server for some hacking or such stuffs. e.g. : www.mysite.com?name=kalpesh can be easily attacked if there is no "htmlentities" which filters all the html tags, by using like : www.mysite.com?name='kalpesh; drop table test;'


what are the various methods to pass data from one web page to another web page ?

GET
HEAD
POST
PUT
DELETE
TRACE
CONNECT
OPTIONS

REF: http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html


What is Template engine in PHP and Hw many types of tables are there in MYSQL database?

MySQL 5.1 supports the following storage engines:

MyISAM

InnoDB

Memory

Merge

Archive

Federated

NDB

CSV

Blackhole


http://dev.mysql.com/doc/refman/5.1/en/storage-engine-overview.html


What is Joomla?

Joomla! is one of the most powerful and an award-winning Open Source Content Management System (CMS) that will help you build everything from simple websites to complex corporate applications. Joomla! is easy to install, simple to manage, and reliable. Best of all, Joomla! is an open source solution that is freely available to everybody.


How to get the URL domain name in PHP?
Yes it is possible by $_server[HTTP_HOST]
eg:

will result the domain name.

What is htaccess? Why do we use this and Where?

Using this ".htaccess" file we can control "php.ini" and "httpd.conf" file.

For php.ini:

for register globals Enter "php_flag register_globals on" in that file and place it inside the context folder where you are running the php files. Now this is set to globals throughout the files present inside that context folder. This is boolean so we are giving like "php_flag". if it is the value we have to give like "php_value".
Added to all answers its also useful for 301 redirection blocking your website for few users can include .php codes on .html file. Still lot more uses are there.

This will allow to have your .php file on .html file

RemoveHandler .html .htm
AddType application/x-httpd-php .php .htm .html

This can block the site for few users.

AuthName "control panel"
AuthType Basic
AuthUserFile /usr/local/bham/.htpasswd

Satisfy any

order deny allow
deny from all
allow from

require user support
require user

use of header() function in php
In commons, header() being used for page redirection, whereby a specific location being define. However header() can be use more than just that.

header() may also be use for page authentication, assigning content type, cache control, etc.