Codeigniter common.php reference error on line 257

Codeigniter is one of the top development frameworks you can find for PHP. CI provides a combination of powerful web applications development features with a very small footprint.

If you are running Codeigniter 2 and recently upgraded to latest PHP version (PHP 5.6.0+ and Apache 2.0+), you have definitely come across the error shown below.

A PHP Error was encountered Severity: Notice 
Message: Only variable references should be returned by reference 
Filename: core/Common.php Line Number: 257

 quick fix/hack

Edit filename: core/Common.php, line number: 257

before

return $_config[0] =& $config;

after

$_config[0] =& $config; 
return $_config[0];