$profileurl = "http://www.linkedin.com/in/".$username;

$fp = curl_init($profileurl);
$response = curl_exec($fp);
$response_code = curl_getinfo($fp,CURLINFO_HTTP_CODE);
$validprofile = ($response_code == 200);

$validprofile将是一个布尔值,指示配置文件是否有效.