DiDom\Query::convertAttribute PHP Method

    protected static function convertAttribute($name, $value)
    {
        $isSimpleSelector = !in_array(substr($name, 0, 1), ['^', '!']);
        $isSimpleSelector = $isSimpleSelector && !in_array(substr($name, -1), ['^', '$', '*', '!', '~']);
        if ($isSimpleSelector) {
            // if specified only the attribute name
            $xpath = $value === null ? '@' . $name : sprintf('@%s="%s"', $name, $value);
            return $xpath;
        }
        // if the attribute name starts with ^
        // example: *[^data-]
        if (substr($name, 0, 1) === '^') {
            $xpath = sprintf('@*[starts-with(name(), "%s")]', substr($name, 1));
            return $value === null ? $xpath : sprintf('%s="%s"', $xpath, $value);
        }
        // if the attribute name starts with !
        // example: input[!disabled]
        if (substr($name, 0, 1) === '!') {
            $xpath = sprintf('not(@%s)', substr($name, 1));
            return $xpath;
        }
        switch (substr($name, -1)) {
            case '^':
                $xpath = sprintf('starts-with(@%s, "%s")', substr($name, 0, -1), $value);
                break;
            case '$':
                $xpath = sprintf('ends-with(@%s, "%s")', substr($name, 0, -1), $value);
                break;
            case '*':
                $xpath = sprintf('contains(@%s, "%s")', substr($name, 0, -1), $value);
                break;
            case '!':
                $xpath = sprintf('not(@%s="%s")', substr($name, 0, -1), $value);
                break;
            case '~':
                $xpath = sprintf('contains(concat(" ", normalize-space(@%s), " "), " %s ")', substr($name, 0, -1), $value);
                break;
        }
        return $xpath;
    }