src/includes/classes/Core/Utils/HtmlWhitespace.php
public function normalize($value, bool $compress = false)
    {
        if (is_array($value) || is_object($value)) {
            foreach ($value as $_key => &$_value) {
                $_value = $this->normalize($_value, $compress);
            } // unset($_key, $_value);
            return $this->c::normalizeEols($value, $compress);
        }
        if (!($string = (string) $value)) {
            return $string; // Nothing to do.
        }
        if (($whitespace = &$this->cacheKey(__FUNCTION__.'_whitespace')) === null) {
            $whitespace = implode('|', $this::HTML_WHITESPACE);
        }
        if ($compress) { // NOTE: This is the only task at the moment. It could change in the future.
            $string = preg_replace('/('.$whitespace.')('.$whitespace.')('.$whitespace.')+/u', '${1}${2}', $string);
        }
        return $this->c::normalizeEols($string, $compress);
    }
public function normalize($value, bool $compress = false)
    {
        if (is_array($value) || is_object($value)) {
            foreach ($value as $_key => &$_value) {
                $_value = $this->normalize($_value, $compress);
            } // unset($_key, $_value);
            return $this->c::normalizeEols($value, $compress);
        }
        if (!($string = (string) $value)) {
            return $string; // Nothing to do.
        }
        if (($whitespace = &$this->cacheKey(__FUNCTION__.'_whitespace')) === null) {
            $whitespace = implode('|', $this::HTML_WHITESPACE);
        }
        if ($compress) { // NOTE: This is the only task at the moment. It could change in the future.
            $string = preg_replace('/('.$whitespace.')('.$whitespace.')('.$whitespace.')+/u', '${1}${2}', $string);
        }
        return $this->c::normalizeEols($string, $compress);
    }
Normalizes HTML whitespace deeply.

@since 150424 Initial release.

@param mixed $value    Any input value.
@param bool  $compress Compress `\n{3,}` into 2?

@return string|array|object With normalized HTML whitespace deeply.