$wxurl='https://open.weixin.qq.com/connect/oauth2/authorize?appid='.$wxwid.'&redirect_uri=http://www.w.com/woauth2.php&response_type=code&scope=snsapi_base&state=1#wechat_redirect';

header('Location: '.$wxurl);

$wxurl = 'https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid='.$wxwid

    .'&secret='.$wxws;

$wxr_code = $_REQUEST['code'];

$wxurl='https://api.weixin.qq.com/sns/oauth2/access_token?appid='.$wxwid

    .'&secret='.$wxws.'&code='.$wxr_code.'&grant_type=authorization_code';

$result = file_get_contents($wxurl);

$res =json_decode($result, true);

var_dump($res);

$wxr_openid=$res['openid'];

var_dump($wxr_openid);