MDL-65175 mlbackend_php: Add missing checking for number of targets

lib/mlbackend/php/classes/processor.php

@@ -291,11 +291,15 @@ class processor implements \core_analytics\classifier, \core_analytics\regressor
 
         // We need at least 2 samples belonging to each target.
         $counts = array_count_values($targets);
+        $ntargets = count(explode(',', $metadata['targetclasses']));
         foreach ($counts as $count) {
             if ($count < 2) {
                 $notenoughdata = true;
             }
         }
+        if ($ntargets > count($counts)) {
+            $notenoughdata = true;
+        }
         if (!empty($notenoughdata)) {
             $resultobj = new \stdClass();
             $resultobj->status = \core_analytics\model::NOT_ENOUGH_DATA;