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    /**
     * Detects an ISO 8601 formatted string.
     *
     * @param string $string
     *
     * @return boolean
     *
     * @see https://developers.facebook.com/docs/graph-api/using-graph-api/#readmodifiers
     * @see http://www.cl.cam.ac.uk/~mgk25/iso-time.html
     * @see http://en.wikipedia.org/wiki/ISO_8601
     */
    public function isIso8601DateString($string)
    {
        // This insane regex was yoinked from here:
        // http://www.pelagodesign.com/blog/2009/05/20/iso-8601-date-validation-that-doesnt-suck/
        // ...and I'm all like:
        // http://thecodinglove.com/post/95378251969/when-code-works-and-i-dont-know-why
        $crazyInsaneRegexThatSomehowDetectsIso8601 = '/^([\+-]?\d{4}(?!\d{2}\b))'
            . '((-?)((0[1-9]|1[0-2])(\3([12]\d|0[1-9]|3[01]))?'
            . '|W([0-4]\d|5[0-2])(-?[1-7])?|(00[1-9]|0[1-9]\d'
            . '|[12]\d{2}|3([0-5]\d|6[1-6])))([T\s]((([01]\d|2[0-3])'
            . '((:?)[0-5]\d)?|24\:?00)([\.,]\d+(?!:))?)?(\17[0-5]\d'
            . '([\.,]\d+)?)?([zZ]|([\+-])([01]\d|2[0-3]):?([0-5]\d)?)?)?)?$/';
        return preg_match($crazyInsaneRegexThatSomehowDetectsIso8601, $string) === 1;
    }