I am writing a script that updates contacts from an external source when their external identifier is equal to the contact being imported. My research shows (and the API explorer confirms) that it should look like this:
'options' => ['match' => "external_identifier"],
I get the error "CiviCRM_API3_Exception: Ambiguous match criteria in civicrm_api3() (line 45 of /var/www/html/sites/all/modules/civicrm/api/api.php)."
Can anyone suggest a solution for what I am doing wrong?