nonBooleanAttribute example

// Special handling for attributes in SVG and MathML.             // Using if/elseif instead of switch because it's faster in PHP.             if ($this->outputMode == static::IM_IN_SVG) {
                $name = Elements::normalizeSvgAttribute($name);
            } elseif ($this->outputMode == static::IM_IN_MATHML) {
                $name = Elements::normalizeMathMlAttribute($name);
            }

            $this->wr(' ')->wr($name);

            if ((isset($val) && '' !== $val) || $this->nonBooleanAttribute($node)) {
                $this->wr('="')->wr($val)->wr('"');
            }
        }
    }

    protected function nonBooleanAttribute(\DOMAttr $attr)
    {
        $ele = $attr->ownerElement;
        foreach ($this->nonBooleanAttributes as $rule) {
            if (isset($rule['nodeNamespace']) && $rule['nodeNamespace'] !== $ele->namespaceURI) {
                continue;
            }