Builds a simple form using the FAPI #pattern proterty.
function form_test_pattern_form($form, &$form_state) {
$form['textfield'] = array(
'#type' => 'textfield',
'#title' => 'One digit followed by lowercase letters',
'#pattern' => '[0-9][a-z]+',
);
$form['tel'] = array(
'#type' => 'tel',
'#title' => 'Everything except numbers',
'#pattern' => '[^\\d]*',
);
$form['password'] = array(
'#type' => 'password',
'#title' => 'Password',
'#pattern' => '[01]+',
);
$form['url'] = array(
'#type' => 'url',
'#title' => 'Client side validation',
'#decription' => 'Just client side validation, using the #pattern attribute.',
'#attributes' => array(
'pattern' => '.*foo.*',
),
'#pattern' => 'ignored',
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => 'Submit',
);
return $form;
}