When your form is submitted, it will pass through a validation function if you define one.  The function name should be nameofyourform_validate($form, &$form_state)

See http://drupal.org/node/751826 (The Drupal forms quickstart guide).

This function will be automatically called when a user submits your form.  Inside this function, you can check on the values of $form and use PHP's is_numeric to be sure that $form_state['ci'] is a numerical value.  If it is not (that is, if is_numeric returns FALSE), use form_set_error to invalidate the submission and return the user to the form page with an error message.

On Thu, Mar 10, 2011 at 11:46 AM, Damian Adriel Perez Valdes <damian.adriel@gmail.com> wrote:
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.