Select Join for two columns in codeigniter

Hello everybody;

Code:

Table 1
   id product_name location added_by updated_by added date
   1  LENOVO       St 23    2        1          2016-08-26

Table 2
id first_name last_name email
1  John       Doe       [email protected]
2  Peter      Smith     [email protected]

I would like to know how to select data with codeigniter query in order to get result like this

Code:

product_name location added_by    updated_by
LENOVO       St 23    Peter Smith John Doe

I have tried with join but added_by column and updated_by column display same data.