Symfony\Component\CssSelector\Parser::parseAttrib PHP Method

    protected function parseAttrib($selector, $stream)
    {
        $attrib = $stream->next();
        if ($stream->peek() == '|') {
            $namespace = $attrib;
            $stream->next();
            $attrib = $stream->next();
        } else {
            $namespace = '*';
        }
        if ($stream->peek() == ']') {
            return new Node\AttribNode($selector, $namespace, $attrib, 'exists', null);
        }
        $op = $stream->next();
        if (!in_array($op, array('^=', '$=', '*=', '=', '~=', '|=', '!='))) {
            throw new SyntaxError(sprintf("Operator expected, got '%s'", $op));
        }
        $value = $stream->next();
        if (!$value->isType('Symbol') && !$value->isType('String')) {
            throw new SyntaxError(sprintf("Expected string or symbol, got '%s'", $value));
        }
        return new Node\AttribNode($selector, $namespace, $attrib, $op, $value);
    }