remove white space

[eluser]Bigil Michael[/eluser]
i want to remove the white space between words

i used validation like this

Code:

array('field'   => 'username','label'   => 'Username', 'rules'   => 'trim|required|xss_clean'),

it accepts username like this bigil michael

i want to remove the white space between bigil & michael

i searched,but no result
can anyone help me????
thanks in advance...........

[eluser]Bigil Michael[/eluser]
solved my pproblem like this

$username = $this->db->escape_str($this->input->post('username'));
$username = str_replace(" ",'',$username);

$data = array(

'username' => $username,

);