code: protected function foreignKeyStringFromArray($dataMember, $opening, $sep = ', ')
      {
          if (empty($this->$dataMember)) {
              return 0;
          }
          //$query = '';
          $count = count($this->$dataMember);
          for($i=0; $i<$count; $i++) {
              $item = $this->{$dataMember}[$i];
              
              $this->query .= ', CONSTRAINT '.'fk_'.$item[0].' FOREIGN KEY ('.$item[0].') REFERENCES '.$item[1].' ('.$item[2].')';
              if ($count-1 != $i) {
                  $this->query .= $sep;
              }
          }
      }
docs: For outputting a string of the following form from the 'foreignKeys' array in Database.
  CONSTRAINT fk_name FOREIGN KEY (name) REFERENCES users (name)