private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
    {
        $data = $cacheItem->get();
        // The isset() is to be removed in 2.0.
        if (!isset($data['createdAt'])) {
            return;
        }

        $modified = new \DateTime('@'.$data['createdAt']);
        $modified->setTimezone(new \DateTimeZone('GMT'));

        return sprintf('%s GMT', $modified->format('l, d-M-y H:i:s'));
    }
private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
    {
        $data = $cacheItem->get();
        // The isset() is to be removed in 2.0.
        if (!isset($data['createdAt'])) {
            return;
        }

        $modified = new \DateTime('@'.$data['createdAt']);
        $modified->setTimezone(new \DateTimeZone('GMT'));

        return sprintf('%s GMT', $modified->format('l, d-M-y H:i:s'));
    }
private function getModifiedSinceHeaderValue ( CacheItemInterface $ cacheItem ) { $ data = $ cacheItem -> get ( ) ; // The isset() is to be removed in 2.0. if ( ! isset ( $ data [ 'createdAt' ] ) ) { return ; } $ modified = new \ DateTime ( '@' . $ data [ 'createdAt' ] ) ; $ modified -> setTimezone ( new \ DateTimeZone ( 'GMT' ) ) ; return sprintf ( '%s GMT' , $ modified -> format ( 'l, d-M-y H:i:s' ) ) ; }
Get the value of the "If-Modified-Since" header.

@param CacheItemInterface $cacheItem

@return string|null
Get the value of the If - Modified - Since header .