original_string: public function set_xaxis(chart_axis $axis, $index = 0) {
          $this->validate_axis('x', $axis, $index);
          return $this->xaxes[$index] = $axis;
      }
code: public function set_xaxis(chart_axis $axis, $index = 0) {
          $this->validate_axis('x', $axis, $index);
          return $this->xaxes[$index] = $axis;
      }
code_tokens: public function set_xaxis ( chart_axis $ axis , $ index = 0 ) { $ this -> validate_axis ( 'x' , $ axis , $ index ) ; return $ this -> xaxes [ $ index ] = $ axis ; }
docstring: Set an X axis.
  
  Note that this will override any predefined axis without warning.
  
  @param chart_axis $axis The axis.
  @param int $index The index of the axis.
docstring_tokens: Set an X axis .