src/Guzzle/Http/Message/Header/CacheControl.php
public function addDirective($param, $value)
    {
        $directives = $this->getDirectives();
        $directives[$param] = $value;
        $this->updateFromDirectives($directives);

        return $this;
    }
public function addDirective($param, $value)
    {
        $directives = $this->getDirectives();
        $directives[$param] = $value;
        $this->updateFromDirectives($directives);

        return $this;
    }
public function addDirective ( $ param , $ value ) { $ directives = $ this -> getDirectives ( ) ; $ directives [ $ param ] = $ value ; $ this -> updateFromDirectives ( $ directives ) ; return $ this ; }
Add a cache control directive

@param string $param Directive to add
@param string $value Value to set

@return self
Add a cache control directive