How to determine whether a remote image exists in PHP

Note: When making a picture preview, I encountered a problem, which is to determine whether the remote file exists (not on the same server).

Examples, multiple methods to determine whether remote images exist.

//Method 1
function file_exists($url)
{
$ch = curl_init();
curl_setopt($ch, curlopt_url,$url);
 curl_setopt($ch, curlopt_nobody, 1); // Do not download
curl_setopt($ch, curlopt_failonerror, 1);
curl_setopt($ch, curlopt_returntransfer, 1);
if(curl_exec( $ch)!==false)
return true;
else
return false;
}
//Method 2
function file_exists2($url)
{
if(file_get_contents($url ,0,null,0,1))
return 1;
else
return 0;
}
//Method 3
function file_exists($url) {
$curl = curl_init($url);
// Not taken Return data
curl_setopt($curl, CURLOPT_NOBODY, true);
//Send request
$result = curl_exec($curl);
$found = false;
//If the request is not sent, it fails
if ($result !== false) {
// Check again whether the http response code is 200
}

Code description: Method 1, returns FALSE regardless of whether the picture is present or not; Method 2 is feasible under Windows. Under LINUX, TRUE will be returned regardless of whether the picture is present or not; Method three should be the most suitable In addition: There are efficiency issues with the get_headers() method, and it is recommended not to use this solution.

fsockopen version:

$url = "http://www.baidu.com/img/baidu_sylogo1.gif";
 $info = parse_url($url);
 $fp = fsockopen($info['host'], 80,$errno, $errstr, 30);
 fputs($fp,"GET {$info['path']} HTTP/ 1.1rn");
 fputs($fp, "Host: {$info['host']}rn");
 fputs($fp, "Connection: closernrn");
 $headers = array();
 while (!feof($fp)) {
 $line = fgets($fp);
 if($line != "rn") {
 $headers[] = $line;
 }else {
 break;
 }
 }
 , for example, responses 302, 301, 404, etc. all mean that the file does not exist. If it is 200, 304, etc., it can be regarded as the file exists.
1. fopen() method: