public function addHeader($header, $value): void
    {
        if ($this->hasHeader($header)) {
            $this->headers[$header][] = $value;
        } else {
            $this->setHeader($header, $value);
        }
    }
public function addHeader($header, $value): void
    {
        if ($this->hasHeader($header)) {
            $this->headers[$header][] = $value;
        } else {
            $this->setHeader($header, $value);
        }
    }
public function addHeader ( $ header , $ value ) : void { if ( $ this -> hasHeader ( $ header ) ) { $ this -> headers [ $ header ] [ ] = $ value ; } else { $ this -> setHeader ( $ header , $ value ) ; } }
Appends a header value for the specified header

Existing values for the specified header will be maintained. The new
value will be appended to the existing list.

@param  string $header header name to add
@param  string $value  value of the header

@return void
Appends a header value for the specified header