protected function _get_thumbnail( $content ) {
		preg_match( '/<meta +?property=["\']og:image["\'][^\/>]*? content=["\']([^"\']+?)["\'].*?\/?>/si', $content, $reg );
		if ( empty( $reg[1] ) ) {
			return;
		}

		$thumbnail = $reg[1];
		$thumbnail = $this->_relative_path_to_url( $thumbnail, $content );

		if ( is_ssl() ) {
			$thumbnail = preg_replace( '|^http:|', 'https:', $thumbnail );
		}

		$requester = new Requester( $thumbnail );
		$response  = $requester->request( $thumbnail );
		if ( is_wp_error( $response ) ) {
			return;
		}

		$status_code = $requester->get_status_code();
		if ( 200 != $status_code && 304 != $status_code ) {
			return;
		}

		return $thumbnail;
	}
protected function _get_thumbnail( $content ) {
		preg_match( '/<meta +?property=["\']og:image["\'][^\/>]*? content=["\']([^"\']+?)["\'].*?\/?>/si', $content, $reg );
		if ( empty( $reg[1] ) ) {
			return;
		}

		$thumbnail = $reg[1];
		$thumbnail = $this->_relative_path_to_url( $thumbnail, $content );

		if ( is_ssl() ) {
			$thumbnail = preg_replace( '|^http:|', 'https:', $thumbnail );
		}

		$requester = new Requester( $thumbnail );
		$response  = $requester->request( $thumbnail );
		if ( is_wp_error( $response ) ) {
			return;
		}

		$status_code = $requester->get_status_code();
		if ( 200 != $status_code && 304 != $status_code ) {
			return;
		}

		return $thumbnail;
	}
protected function _get_thumbnail ( $ content ) { preg_match ( '/<meta +?property=["\']og:image["\'][^\/>]*? content=["\']([^"\']+?)["\'].*?\/?>/si' , $ content , $ reg ) ; if ( empty ( $ reg [ 1 ] ) ) { return ; } $ thumbnail = $ reg [ 1 ] ; $ thumbnail = $ this -> _relative_path_to_url ( $ thumbnail , $ content ) ; if ( is_ssl ( ) ) { $ thumbnail = preg_replace ( '|^http:|' , 'https:' , $ thumbnail ) ; } $ requester = new Requester ( $ thumbnail ) ; $ response = $ requester -> request ( $ thumbnail ) ; if ( is_wp_error ( $ response ) ) { return ; } $ status_code = $ requester -> get_status_code ( ) ; if ( 200 != $ status_code && 304 != $ status_code ) { return ; } return $ thumbnail ; }
Return thumbnail of the page you want to blog card

@param string $content
@return string
Return thumbnail of the page you want to blog card