When validating a custom field, and the test fails, Joomla returns the following default error message:

**Warning** Invalid field: My Field

How can I specify the message that is returned to explain why it is invalid?


Add the message attribute, but better like this:

<field name="my_code" type="text" size="15" label="My Code"
  validate="myrule" message="Field may only contain A-z or 0-9" />


  • didn't work. i've place the attribute with custom message but all i see is Invalid field: Title when submit.
    – R T
    Mar 30 '15 at 10:11
  • Agree with prev comment. Doesn't work on Joomla 3.6.5. Is the behaviour dependent on the template used? Sep 15 '17 at 8:02

For an message that may vary, add the message attribute like this:

public function test(SimpleXMLElement $element, $value, $group = null, JRegistry $input = null, JForm $form = null)
    if(!preg_match('/^[a-z0-9]+$/i', $value)) {
        $element->addAttribute('message', 'Field may only contain A-z or 0-9');
        return false;
    }elseif(!$somethingelse) {
        $element->addAttribute('message', 'Something else is wrong');
        return false;

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