Database connection "Mysql" is missing, or could not be created. in Cake PHP

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PHP

MySQL

XAMPP

Cake is NOT able to connect to the database.

Database connection "Mysql" is missing, or could not be created.
SQLSTATE[42000] [1044] Access denied for user ''@'localhost' to database 'database_name'

Above is the error message rise when i use Cake php and Mysql (in XAMPP)in windows 7

but i use simple code

<?php
// Create connection
$con=mysqli_connect("localhost","root","","database_name");

// Check connection
if (mysqli_connect_errno($con))
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
 else
  {
   echo "connected to MySQL " ;
  } 
?> 

[^] but this code worked fine ..
how can i connect to mysql database in cake php ?
i want connect database how it could be possible ?