src/Baum/SetBuilder.php
protected function getNextBound($key) {
    if ( false === array_key_exists($key, $this->bounds) )
      $this->bounds[$key] = 0;

    $this->bounds[$key] = $this->bounds[$key] + 1;

    return $this->bounds[$key];
  }
protected function getNextBound($key) {
    if ( false === array_key_exists($key, $this->bounds) )
      $this->bounds[$key] = 0;

    $this->bounds[$key] = $this->bounds[$key] + 1;

    return $this->bounds[$key];
  }
Return next index bound value for the given key (current scope identifier)

@param   string  $key
@return  integer