public function set(string $header, string $value) : void
    {
        $this->headers[$header] = $value;
    }
public function set(string $header, string $value) : void
    {
        $this->headers[$header] = $value;
    }
public function set ( string $ header , string $ value ) : void { $ this -> headers [ $ header ] = $ value ; }
Set or override header.

@param string $header
@param string $value
@return void
Set or override header .