lib/classes/Swift/Mime/SimpleHeaderSet.php
public function set(Swift_Mime_Header $header, $index = 0)
    {
        $this->storeHeader($header->getFieldName(), $header, $index);
    }
public function set(Swift_Mime_Header $header, $index = 0)
    {
        $this->storeHeader($header->getFieldName(), $header, $index);
    }
public function set ( Swift_Mime_Header $ header , $ index = 0 ) { $ this -> storeHeader ( $ header -> getFieldName ( ) , $ header , $ index ) ; }
Set a header in the HeaderSet.

The header may be a previously fetched header via {@link get()} or it may
be one that has been created separately.

If $index is specified, the header will be inserted into the set at this
offset.

@param int $index
Set a header in the HeaderSet .