Solve Error(Message: Only variable references should be returned by reference) in Codeighter

When we install codeigniter framework then show error message after installation, how to solved above error in codeigniter framework below step.

Step 1

File Path: root\system\core\Common.php

open Common.php file and find get_config function into file.

if ( ! function_exists('get_config'))
{
function &get_config($replace = array())
{
static $_config;
if (isset($_config))
{
return $_config[0];
}
// Is the config file in the environment folder?
if ( ! defined('ENVIRONMENT') OR ! file_exists($file_path = APPPATH.'config/'.ENVIRONMENT.'/config.php'))
{
$file_path = APPPATH.'config/config.php';
}
// Fetch the config file
if ( ! file_exists($file_path))
{
exit('The configuration file does not exist.');
}
require($file_path);
// Does the $config array exist in the file?
if ( ! isset($config) OR ! is_array($config))
{
exit('Your config file does not appear to be formatted correctly.');
}
// Are any values being dynamically replaced?
if (count($replace) > 0)
{
foreach ($replace as $key => $val)
{
if (isset($config[$key]))
{
$config[$key] = $val;
}
}
}
return $_config[0] =& $config;
}
}

Replace code

if ( ! function_exists('get_config'))
{
function &get_config($replace = array())
{
static $_config;
if (isset($_config))
{
return $_config[0];
}
// Is the config file in the environment folder?
if ( ! defined('ENVIRONMENT') OR ! file_exists($file_path = APPPATH.'config/'.ENVIRONMENT.'/config.php'))
{
$file_path = APPPATH.'config/config.php';
}
// Fetch the config file
if ( ! file_exists($file_path))
{
exit('The configuration file does not exist.');
}
require($file_path);
// Does the $config array exist in the file?
if ( ! isset($config) OR ! is_array($config))
{
exit('Your config file does not appear to be formatted correctly.');
}
// Are any values being dynamically replaced?
if (count($replace) > 0)
{
foreach ($replace as $key => $val)
{
if (isset($config[$key]))
{
$config[$key] = $val;
}
}
}
$_config[0] =& $config;
return $_config[0];
}
}

and refresh page.