public function getHeader($header): string
    {
        if ($this->hasHeader($header)) {
            return implode(', ', $this->headers[$header]);
        }
        return '';
    }
public function getHeader($header): string
    {
        if ($this->hasHeader($header)) {
            return implode(', ', $this->headers[$header]);
        }
        return '';
    }
public function getHeader ( $ header ) : string { if ( $ this -> hasHeader ( $ header ) ) { return implode ( ', ' , $ this -> headers [ $ header ] ) ; } return '' ; }
Retrieve a header by the given case-insensitive name as a string

This method returns all of the header values of the given
case-insensitive header name as a string concatenated together using
a comma.

@param  string $header case-insensitive header name.

@return string
Retrieve a header by the given case - insensitive name as a string