<?php namespace MailPoetVendor\Sabberworm\CSS\Property; if (!defined('ABSPATH')) exit; class KeyframeSelector extends Selector { const SELECTOR_VALIDATION_RX = '/ ^( (?: [a-zA-Z0-9\\x{00A0}-\\x{FFFF}_^$|*="\'~\\[\\]()\\-\\s\\.:#+>]* # any sequence of valid unescaped characters (?:\\\\.)? # a single escaped character (?:([\'"]).*?(?<!\\\\)\\2)? # a quoted text like [id="example"] )* )| (\\d+%) # keyframe animation progress percentage (e.g. 50%) $ /ux'; }