HTMLPurifier_PercentEncoder::__construct PHP Method

    public function __construct($preserve = false)
    {
        // unreserved letters, ought to const-ify
        for ($i = 48; $i <= 57; $i++) {
            // digits
            $this->preserve[$i] = true;
        }
        for ($i = 65; $i <= 90; $i++) {
            // upper-case
            $this->preserve[$i] = true;
        }
        for ($i = 97; $i <= 122; $i++) {
            // lower-case
            $this->preserve[$i] = true;
        }
        $this->preserve[45] = true;
        // Dash         -
        $this->preserve[46] = true;
        // Period       .
        $this->preserve[95] = true;
        // Underscore   _
        $this->preserve[126] = true;
        // Tilde        ~
        // extra letters not to escape
        if ($preserve !== false) {
            for ($i = 0, $c = strlen($preserve); $i < $c; $i++) {
                $this->preserve[ord($preserve[$i])] = true;
            }
        }
    }