Rejecting input without a leading zero

In this recipe, we will add a rule that requires a valid number to be entered, without a leading digit, 0. This is useful for validating whole numbers without zero padding.

Getting ready

Please refer to the first recipe in this chapter for details on how to prepare a QuickForm web form which is the basis of this recipe.

How to do it...

Add the following code to our form definition in validation_form.php, just after the field definition:

$mform->addElement('text', 'mytext11', 'No leading zero');
$mform->addRule('mytext11', 'No leading zero', 'nonzero', null, 'client');

Now we can test the rule by adding an invalid sequence of digits with a leading zero: 0123. We see that our validation warning message is displayed and we are unable to submit the form as seen in the following screenshot:

How it works...

We used the validation type nonzero which does not require any format options. Now when a user attempts to enter text that contains a leading zero, a...