Checks whether a string is a valid JSON Media Type.

function wp_is_json_media_type( $media_type ) {
	static $cache = array();

	if ( ! isset( $cache[ $media_type ] ) ) {
		$cache[ $media_type ] = (bool) preg_match( '/(^|s|,)application/([w!#$&-^.+]++)?json(+oembed)?($|s|;|,)/i', $media_type );
	}

	return $cache[ $media_type ];
}