PHP detects if a remote file exists

<?php

$url = ' http://example.com ';

$hander _array = get_headers ($url);

if ($header _array [0] = = ' http/1.1 OK ') {

echo ' file exists ';

} else {

Echo ' file does not exist ';

}

Simply explain the above code. The function of get_headers is to access a remote address and return the HTTP headers sent by the server as an array. The $header[0] is the status code returned by the server (the status code should be the first to return if not unexpectedly).

To determine the existence of a file on the remote server, just make sure that the status code returned by accessing the file is "http/1.1" (of course you can also tell if the status code is not "http/1.1 404 Not Found" Then the file exists, but the total feeling is not insured, There are, after all, other status codes such as 301,400.

Get an example of a three-bit HTTP response code:

<?php  function Get_http_response_code ($theURL) {      $headers = get_headers ($theURL);      return substr ($headers [0], 9, 3);  }  ? >

Examples of excluding redirects:

<?php  /**  * Fetches all the real headers sent by the server in response to a HTTP request without redirects
  
   * gets a header that does not contain a redirect  */     function get_real_headers ($url, $format =0, $follow _redirect=0) {    if (! $follow _redirect {      //set new default options      $opts = Array (' http ' = = =          Array (' max_redirects ' =>1, ' ignore_errors ' = =) 1)      );      Stream_context_get_default ($opts);    }    Get headers      $headers =get_headers ($url, $format);      Restore default Options    if (Isset ($opts)) {      $opts = array (' http ' = =          Array (' Max_redirects ' =>20, ' Ignore_errors ' =>0)      );      Stream_context_get_default ($opts);    }    return      return $headers;  }  ? >
  

