Get Contact id from Relationship to use in a Hook [duplicate]

Question

I want to display Contact B ID of a relationship for the current contact. I am building a hook and this is my code so far.

if ( $formName == 'CRM_Contactlayout_Form_Inline_ProfileBlock') {
        if ($form == CRM_Core_Action::ADD) {
            $ID= '190';
            $defaults['custom_189'] = $ID;
            $form->updateElementAttr('custom_189',array('readonly'));
    }

I want to replace 190 with a code that grabs the contact ID of that current users relationship.

Your help is much appreciated.

Thanks

Answer 1

This code worked for me:

$contactId = CRM_Utils_Request::retrieve('cid', 'Positive');