Validating Fax Number

Last updated on

30 April 2025

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  $fax = $form_values['submitted_tree']['fax'];
  if (strlen(trim($fax)) > 0) {
    if (!ereg("^[0-9]{1,3}-[0-9]{3}-[0-9]{3,4}-[0-9]{3,4}$";, $fax)) {
      form_set_error('submitted][fax', t('Fax number must be in format xxx-xxx-nnnn-nnnn.'));
    }
  }

The if (strlen(trim($fax)) > 0) { line ensures the number is optional for the end-user.

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