Adding a field that accepts only alphanumeric characters

In this recipe, we will add a rule that accepts only alphanumeric characters, that is, only the digits 0-9 and letters a-z in upper or lower case.

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', 'mytext8', 'Alpha-numeric');
$mform->addRule('mytext8', 'Alpha-numeric', 'alphanumeric', null, 'client');

Now we can test this new rule by entering text including non-alphanumeric characters. In the following example, we have enclosed our text in non-alphanumeric double quotes. We see that the 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 alphanumeric which does not require any format options. When...