PHP利用get_headers()函数判断远程的url地址是否有效

$url = "https://www.baidu.com";
$response = get_headers($url);
echo "<pre>";
var_dump($response);
$response = get_headers($url,1);//如果将可选的 format 参数设为 1，则 get_headers() 会解析相应的信息并设定数组的键名。
echo ‘<pre>‘;
var_dump($response);

array(16) {
  [0]=>string(15) "HTTP/1.0 200 OK"
  [1]=>string(20) "Accept-Ranges: bytes"
  [2]=>string(23) "Cache-Control: no-cache"
  [3]=>string(21) "Content-Length: 14722"
  [4]=>string(23) "Content-Type: text/html"
  [5]=>string(35) "Date: Wed, 20 Feb 2019 13:12:31 GMT"
  [6]=>string(21) "Etag: "5c653bc8-3982""
  [7]=>string(44) "Last-Modified: Thu, 14 Feb 2019 09:58:32 GMT"
  [8]=>string(39) "P3p: CP=" OTI DSP COR IVA OUR IND COM ""
  [9]=>string(16) "Pragma: no-cache"
  [10]=>string(15) "Server: BWS/1.1"
  [11]=>string(141) "Set-Cookie: BAIDUID=72E4B8623F9E998C790B22F8E8D64BEC:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com"
  [12]=>string(137) "Set-Cookie: BIDUPSID=72E4B8623F9E998C790B22F8E8D64BEC; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com"
  [13]=>string(111) "Set-Cookie: PSTM=1550668351; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com"
  [14]=>string(21) "Vary: Accept-Encoding"
  [15]=>string(33) "X-Ua-Compatible: IE=Edge,chrome=1"
}

array(14) {
  [0]=>string(15) "HTTP/1.0 200 OK"
  ["Accept-Ranges"]=>string(5) "bytes"
  ["Cache-Control"]=>string(8) "no-cache"
  ["Content-Length"]=>string(5) "14722"
  ["Content-Type"]=>string(9) "text/html"
  ["Date"]=>string(29) "Wed, 20 Feb 2019 13:12:31 GMT"
  ["Etag"]=>string(15) ""5c653bc8-3982""
  ["Last-Modified"]=>string(29) "Thu, 14 Feb 2019 09:58:32 GMT"
  ["P3p"]=>string(34) "CP=" OTI DSP COR IVA OUR IND COM ""
  ["Pragma"]=>string(8) "no-cache"
  ["Server"]=>string(7) "BWS/1.1"
  ["Set-Cookie"]=>array(3) {
    [0]=>string(129) "BAIDUID=72E4B8623F9E998CF68FDDAD465EAF4A:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com"
    [1]=>string(125) "BIDUPSID=72E4B8623F9E998CF68FDDAD465EAF4A; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com"
    [2]=>string(99) "PSTM=1550668351; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com"
  }
  ["Vary"]=>string(15) "Accept-Encoding"
  ["X-Ua-Compatible"]=>string(16) "IE=Edge,chrome=1"
}

$url = "https://www.baidu.com";
$response = get_headers($url);
if(preg_match(‘/200/‘,$response[0])){ 
    echo "<pre/>"; 
    var_dump($response[0]); 
}else{ 
   var_dump("无效url资源！"); 
}

string(15) "HTTP/1.0 200 OK"