[development] Form Textfield numeric

[Damian Adriel Perez Valdes]

Hello:

I need your help. I'm making a Drupal module, and i need to validate if the
textfield data are numeric or not. can i use a drupal functions for this ?

This is my form code:

            'ci' => array (
                '#title' => t('C.I.'),
                '#type' => 'textfield',
                '#maxlength' => 11,
                '#size' => 20,
                '#required' => TRUE,
            ),

Thanks.