php简单的html dom解析器在一个文件中扫描多个页面时返回错误500

Question

My code works well when I just only crawl one website. If I crawl two website in a single php file, it will result in a 500 Server Error.

Here is my functuin. I call this function twice in my code.

function scan_wedsite(&$array, $url) {
    $string = file_get_contents($url);
    $html = new simple_html_dom();
    $html->load($string);

    foreach($html->find('tr[valign=top]') as $item) {
        /*  find the data and store it into $element  */
        array_push($array, $element);
    }

    $html->clear();
    unset($html);
}

Can anyone help me to solve this problem?