public function setDefaultHeader(string $name, string $value) {
        $this->defaultHeaders[$name] = $value;
        return $this;
    }
public function setDefaultHeader(string $name, string $value) {
        $this->defaultHeaders[$name] = $value;
        return $this;
    }
public function setDefaultHeader ( string $ name , string $ value ) { $ this -> defaultHeaders [ $ name ] = $ value ; return $ this ; }
Set the value of a default header.

@param string $name The name of the header to set.
@param string $value The new value of the default header.
@return HttpClient Returns `$this` for fluent calls.
Set the value of a default header .