How to Enable CURL in WAMP?

CURL is not enabled by default in WAMP. Every php programmer have to use CURL to make remote connection.

The steps are as follows :

1) Close WAMP (if running)
2) Navigate to WAMP\bin\php\(your version of php)\
3) edit php.ini
4) Search for curl, uncomment extension=php_curl.dll
5) Navigate to WAMP\bin\Apache\(your version of apache)\bin\
6) edit php.ini
7) Search for curl, uncomment extension=php_curl.dll
8 ) Save both
9) Restart WAMP

That will solve your Curl issues.
Enjoy!

Perl Interview Questions?

What is use of ‘strict’ in perl ?
The module strict restricts ‘unsafe constructs’, according to the perldocs
When you enable the strict module, the three things that Perl becomes strict about are:
• Variables ‘vars’
• References ‘refs’
• Subroutines ‘subs’
Strict variables are useful. Essentially, this means that all variables must be declared, that is defined before use. Furthermore, each variable must be defined with my or fully qualified

What is scalars in perl ?
The most basic kind of variable in Perl is the scalar variable. Scalar variables hold both strings and numbers, and are remarkable in that strings and numbers are completely interchangable. For example, the statement
$priority = 9;
sets the scalar variable $priority to 9, but you can also assign a string to exactly the same variable:
$priority = ‘high’

Perl difference between lists and arrays ?
A list is a fixed collection of scalars. An array is a variable that holds a variable collection of scalars.
Array operations, which change the scalars, reaaranges them, or adds or subtracts some scalars, only work on arrays. These can’t work on a list, which is fixed. Array operations include shift, unshift, push, pop, and splice.
You can change an array element, but you can’t change a list element.

What is the use of ‘defined’?
defined EXPR
defined

Returns true if EXPR has a value other than the undef value, or checks the value of $_ if EXPR is not specified.
If EXPR is a function or function reference, then it returns true if the function has been defined.

Return Value
• 0 if EXPR contains undef
• 1 if EXPR contains a valid value or reference

#!/usr/bin/perl
$var1 = "This is defined";
if( defined($var1) ){
  print "$var1\n";
}
if( defined($var2) ){
  print "var2 is also defined\n";
}else{
  print "var2 is not defined\n";
}
This will produce following result
This is defined
var2 is not defined

Perl 5 cheat sheet

This ‘cheat sheet’ is a handy reference, meant for beginning Perl programmers. Not everything is mentioned, but 195 features may already be overwhelming.

Perl 5 cheat sheet v8

 CONTEXTS  SIGILS             ARRAYS        HASHES
 void      $scalar   whole:   @array        %hash
 scalar    @array    slice:   @array[0, 2]  @hash{'a', 'b'}
 list      %hash     element: $array[0]     $hash{'a'}
           &sub
           *glob    SCALAR VALUES
                    number, string, reference, glob, undef
 REFERENCES
 \     references      $$foo[1]       aka $foo->[1]
 $@%&* dereference     $$foo{bar}     aka $foo->{bar}
 []    anon. arrayref  ${$$foo[1]}[2] aka $foo->[1]->[2]
 {}    anon. hashref   ${$$foo[1]}[2] aka $foo->[1][2]
 \()   list of refs
                         NUMBERS vs STRINGS  LINKS
 OPERATOR PRECEDENCE     =          =        perl.plover.com
 ->                      +          .        search.cpan.org
 ++ --                   == !=      eq ne         cpan.org
 **                      < > <= >=  lt gt le ge   pm.org
 ! ~ \ u+ u-             <=>        cmp           tpj.com
 =~ !~                                            perldoc.com
 * / % x                 SYNTAX
 + - .                   for    (LIST) { }, for (a;b;c) { }
 << >>                   while  ( ) { }, until ( ) { }
 named uops              if     ( ) { } elsif ( ) { } else { }
 < > <= >= lt gt le ge   unless ( ) { } elsif ( ) { } else { }
 == != <=> eq ne cmp     for equals foreach (ALWAYS)
 &

 | ^              REGEX METACHARS            REGEX MODIFIERS
 &&               ^     string begin         /i case insens.
 ||               $     str. end (before \n) /m line based ^$
 .. ...           +     one or more          /s . includes \n
 ?:               *     zero or more         /x ign. wh.space
 = += -= *= etc.  ?     zero or one          /g global
 , =>             {3,7} repeat in range
 list ops         ()    capture          REGEX CHARCLASSES
 not              (?:)  no capture       .  == [^\n]
 and              []    character class  \s == [\x20\f\t\r\n]
 or xor           |     alternation      \w == [A-Za-z0-9_]
                  \b    word boundary    \d == [0-9]
                  \z    string end       \S, \W and \D negate
 DO
 use strict;        DON'T            LINKS
 use warnings;      "$foo"           perl.com
 my $var;           $$variable_name  perlmonks.org
 open() or die $!;  `$userinput`     use.perl.org
 use Modules;       /$userinput/     perl.apache.org
                                     parrotcode.org
 FUNCTION RETURN LISTS
 stat      localtime    caller         SPECIAL VARIABLES
  0 dev    0 second     0 package      $_    default variable
  1 ino    1 minute     1 filename     $0    program name
  2 mode   2 hour       2 line         $/    input separator
  3 nlink  3 day        3 subroutine   $\    output separator
  4 uid    4 month-1    4 hasargs      $|    autoflush
  5 gid    5 year-1900  5 wantarray    $!    sys/libcall error
  6 rdev   6 weekday    6 evaltext     $@    eval error
  7 size   7 yearday    7 is_require   $$    process ID
  8 atime  8 is_dst     8 hints        $.    line number
  9 mtime               9 bitmask      @ARGV command line args
 10 ctime  just use                    @INC  include paths
 11 blksz  POSIX::      3..9 only      @_    subroutine args
 12 blcks  strftime!    with EXPR      %ENV  environment

How to prevent XSS attacks through php?

There are a number of ways hackers put to use for XSS attacks, PHP’s built-in functions do not respond to all sorts of XSS attacks. Hence, functions such as strip_tags, filter_var, mysql_real_escape_string, htmlentities, htmlspecialchars, etc do not protect us 100%. You need a better mechanism, here is what is solution:

<?php 
function xss_clean($data)
{
// Fix &entity\n;
$data = str_replace(array('&amp;','&lt;','&gt;'), array('&amp;amp;','&amp;lt;','&amp;gt;'), $data);
$data = preg_replace('/(&#*\w+)[\x00-\x20]+;/u', '$1;', $data);
$data = preg_replace('/(&#x*[0-9A-F]+);*/iu', '$1;', $data);
$data = html_entity_decode($data, ENT_COMPAT, 'UTF-8');
 
// Remove any attribute starting with "on" or xmlns
$data = preg_replace('#(<[^>]+?[\x00-\x20"\'])(?:on|xmlns)[^>]*+>#iu', '$1>', $data);
 
// Remove javascript: and vbscript: protocols
$data = preg_replace('#([a-z]*)[\x00-\x20]*=[\x00-\x20]*([`\'"]*)[\x00-\x20]*j[\x00-\x20]*a[\x00-\x20]*v[\x00-\x20]*a[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#iu', '$1=$2nojavascript...', $data);
$data = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*v[\x00-\x20]*b[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#iu', '$1=$2novbscript...', $data);
$data = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*-moz-binding[\x00-\x20]*:#u', '$1=$2nomozbinding...', $data);
 
// Only works in IE: <span style="width: expression(alert('Ping!'));"></span>
$data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?expression[\x00-\x20]*\([^>]*+>#i', '$1>', $data);
$data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?behaviour[\x00-\x20]*\([^>]*+>#i', '$1>', $data);
$data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:*[^>]*+>#iu', '$1>', $data);
 
// Remove namespaced elements (we do not need them)
$data = preg_replace('#</*\w+:\w[^>]*+>#i', '', $data);
 
do
{
        // Remove really unwanted tags
        $old_data = $data;
        $data = preg_replace('#</*(?:applet|b(?:ase|gsound|link)|embed|frame(?:set)?|i(?:frame|layer)|l(?:ayer|ink)|meta|object|s(?:cript|tyle)|title|xml)[^>]*+>#i', '', $data);
}
while ($old_data !== $data);
 
// we are done...
return $data;
}
?>

MYSQL data manipulation language (DML) commands?

Data Manipulation Language

Data Manipulation Language (DML) statements are used for managing data within tables. Some commands of DML are:

 
1. SELECT - retrieve data from the a database
2. INSERT - insert data into a table
3. UPDATE - updates existing data within a table
4. DELETE - deletes all records from a table, the space for the records remain
5. MERGE - UPSERT operation (insert or update)
6. CALL - call a PL/SQL or Java/php subprogram
7. LOCK TABLE - control concurrency