Concate two post variables

[eluser]Noah_Igniter[/eluser]

Code:

$inputdata['first_name'] = $this->input->post('first_name');
       $inputdata['last_name'] = $this->input->post('last_name');

i need to concate the two variables and save in table as "display_name"
please help me

[eluser]solid9[/eluser]
$fname = $this->input->post('first_name');
$lname = $this->input->post('last_name');

$this->data['fullname'] = $fname.$lname;