Php code in field validation UI

change your code to:

if ($this->value == 'abc'){
   $this->set_error();
} 

Hi,

I cracked it, here's the confirm solution.

Issue you are facing may happen due to your disabled field validation UI module and/OR validation rules. If not then please refer below example:

if($this->value == 'abc'){
$token = array('[mytest]' => 'abc');
$this->set_error($token);
}

We could pass some tokens to error message.

It is very simple.
we could get the current value using
"$this->value, "

could set error the message using
"$this->set_error();"

Could set the error message through a token
"$this->set_error($token);"

You can also use available variables:
$this->entity_type ;
$this->entity ;
$this->field;
$this->instance;
$this->langcode;
$this->items ;
$this->delta;
$this->item ;
$this->value ;
$this->rule ;

if we need to set an error, just call "$this->set_error();". If it does not work as you expected, you could call "form_set_error()" directly.

The best way to use you could visit it through "$this->entity->field_another_field_against" rather then you use 'abc' hardcode value.

But need to check first that your $this->value contain as you defined into IF conditional statement (i.e. 'abc').

Hope this helps!

Thanks

I used this code to validate the dete of death is not before the date of birth..
if ($this->value < $this->entity->field_dobirth["und"][0]["value"]) {
$this->set_error();
{
But it doesn't work at all. variables r correct.