A PHP Error was encountered Severity: Notice Message: Only variables should be passed by reference

Question

i have a website with the following error in Codeigniter:

A PHP Error was encountered Severity: Notice

Message: Only variables should be passed by reference

Filename: core/Common.php

Line Number: 166

This is the line.....

    $_classes[$class] = instantiate_class(new $name());
    return $_classes[$class];
}