How i can get ip address?

We can use SERVER var $_SERVER['SERVER_ADDR'] and getenv("REMOTE_ADDR") and $_SERVER['REMOTE_ADDR'] functions to get the IP address.


<?php
echo $_SERVER['SERVER_ADDR'];
echo $_SERVER['REMOTE_ADDR'];
echo getenv("REMOTE_ADDR");
?>

What is the difference between htmlentities() and htmlspecialchars()

htmlspecialchars() – Convert some special characters to HTML entities (Only the most widely used)

htmlentities() – Convert ALL special characters to HTML entities

<?php

$str = "A 'quote' is <b>bold</b>";

echo htmlentities($str);

echo htmlentities($str, ENT_QUOTES);

?>

htmlspecialchars — Convert special characters to HTML entities

htmlspecialchars only takes care of <, >, single quote ‘, double quote " and ampersand.

<?php

$new = htmlspecialchars("<a href='test'>Test</a>", ENT_QUOTES);

echo $new;

?> 

functions to sorting an array elements

The following functions are used sorting an array elements
Sort(),          arsort(),

asort(),          ksort(),

rsort(),          usort()

array_multisort() & uksort()

What are the differences between public, private, protected, static, transient, final and volatile?

Public: Public declared items can be accessed everywhere.
 
Protected: Protected limits access to inherited and parent classes (and to the class that defines the item).

Private: Private limits visibility only to the class that defines the item.
 
Static: A static variable exists only in a local function scope,but it does not lose its value when program execution leaves this scope.

Final: Final keyword prevents child classes from overriding a method by prefixing the definition with final. If the class itself is being defined final then it cannot be extended.

transient: A transient variable is a variable that may not be serialized.

volatile: a variable that might be concurrently modified by multiple threads should be declared volatile. Variables declared to be volatile will not be optimized by the compiler because their value can change at any time.

What is meant by nl2br()?

Inserts HTML line breaks (<BR />) before all newlines in a string
string nl2br (string); Returns string with ” inserted before all
newlines.

For example: 

echo nl2br(“god bless\n you”);

will output “god

bless <br /> you” to your browser

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?

When to use GET or POST

The HTML 2.0 specification says, in section Form
Submission (and the HTML 4.0 specification repeats this with minor
stylistic changes):

–>If the processing of a form is idempotent
(i.e. it has no lasting observable effect on the state of the
world), then the form method should be GET. Many database searches
have no visible side-effects and make ideal applications of query
forms.
–
–>If the service associated with the processing of a form has side
effects (for example, modification of a database or subscription to
a service), the method should be POST.

How the form data is transmitted?

quotation from the HTML 4.0 specification

–> If the method is “get” – -, the user agent
takes the value of action, appends a ? to it, then appends the form
data set, encoded using the application/x-www-form-urlencoded
content type. The user agent then traverses the link to this URI. In
this scenario, form data are restricted to ASCII codes.
–> If the method is “post” –, the user agent conducts an HTTP post
transaction using the value of the action attribute and a message
created according to the content type specified by the enctype
attribute.

Quote from CGI FAQ

Firstly, the the HTTP protocol specifies
differing usages for the two methods. GET requests should always be
idempotent on the server. This means that whereas one GET request
might (rarely) change some state on the Server, two or more
identical requests will have no further effect.

This is a theoretical point which is also good
advice in practice. If a user hits “reload” on his/her browser, an
identical request will be sent to the server, potentially resulting
in two identical database or
guestbook entries, counter increments, etc. Browsers may reload a
GET URL automatically, particularly if cacheing is disabled (as is
usually the case with CGI output), but will typically prompt the
user before
re-submitting a POST request. This means you’re far less likely to
get inadvertently-repeated entries from POST.

GET is (in theory) the preferred method for
idempotent operations, such as querying a database, though it
matters little if you’re using a form. There is a further practical
constraint that many systems have built-in limits to the length of a
GET request they can handle: when the total size of a request (URL+params)
approaches or exceeds 1Kb, you are well-advised to use POST in any
case.

I would prefer POST when I don’t want the status to
be change when user resubmits. And GET
when it does not matter.

display PHP errors in My Script Code When display_errors is Disabled

ometimes, your head turns trying to figure out what the problem is with your script. many times when the display_errors if off, you won't have a clue as to what the problem is unless you display the php errors.

this is how the php.ini file would look like:



     Quote:
; - display_errors = Off [Security]
; With this directive set to off, errors that occur during the execution of
; scripts will no longer be displayed as a part of the script output, and thus,
; will no longer be exposed to remote users. With some errors, the error message
; content may expose information about your script, web server, or database
; server that may be exploitable for hacking. Production sites should have this
; directive set to off.

; Print out errors (as a part of the output). For production web sites,
; you're strongly encouraged to turn this feature off, and use error logging
; instead (see below). Keeping display_errors enabled on a production web site
; may reveal security information to end users, such as file paths on your Web
; server, your database schema or other information.
display_errors = On

copy and paste this code

ini_set('display_errors', 1);
ini_set('log_errors', 1);
ini_set('error_log', dirname(__FILE__) . '/error_log.txt');
error_reporting(E_ALL);