How to use the get_headers function in PHP to determine whether a remote file exists, _PHP tutorial

How PHP uses the get_headers function to determine whether a remote file exists,

The example in this article describes how PHP uses the get_headers function to determine whether a remote file exists. Share it with everyone for your reference. The specific implementation method is as follows:

Previous articles about the process of determining whether remote files exist in PHP all used fopen, sockt, and curl functions to check whether remote files exist. Now I will introduce how to use get_headers to check whether remote files exist. Interested friends can For reference.

First let’s briefly understand the get_headers() function

get_headers() returns an array m containing the headers sent by the server in response to an HTTP request.

get_headers: Send server response to HTTP request

get_headers(string url[link format])

get_headers() returns the server HTTP request m in the form of an array. If the execution fails, it will return FALSE and an error level E_WARNING,

The optional parameter is set to 1, get_headers() can analyze the response speed of the system and the keys in the set array,

Note: To use this function, you need to set allow_url_fopen = On in php.ini to use

The example code is as follows:

Copy code The code is as follows:

<?php
$url = 'http://www.bkjia.com';
print_r(get_headers($url));
print_r(get_headers($url, 1));
?>

The running results are as follows:

Copy code The code is as follows:

Array
(
[0] => HTTP/1.1 200 OK
[1] => Cache-Control: max-age=1800
[2] => Content-Length: 54874
[3] => Content-Type: text/html
[4] => Content-Location: http://www.bkjia.com/index.htm
[5] => Last-Modified: Fri, 28 Nov 2014 03:34:56 GMT
[6] => Accept-Ranges: bytes
[7] => ETag: "b66ba847bcad01:bc5"
[8] => Server: Microsoft-IIS/6.0
[9] => Date: Fri, 28 Nov 2014 03:37:34 GMT
[10] => Connection: close
)
Array
(
[0] => HTTP/1.1 200 OK
[Cache-Control] => max-age=1800
[Content-Length] => 54874
[Content-Type] => text/html
[Content-Location] => http://www.bkjia.com/index.htm
[Last-Modified] => Fri, 28 Nov 2014 03:34:56 GMT
[Accept-Ranges] => bytes
[ETag] => "b66ba847bcad01:bc5"
[Server] => Microsoft-IIS/6.0
[Date] => Fri, 28 Nov 2014 03:37:35 GMT
[Connection] => close
)

The code to determine whether the remote file exists is as follows:

Copy the code The code is as follows:

//Determine whether the remote file exists
function remote_file_exists($url) {
          $executeTime = ini_get('max_execution_time');                                    ini_set('max_execution_time', 0);
          $headers = @get_headers($url);                                          ini_set('max_execution_time', $executeTime);
If ($headers) {
                 $head = explode(' ', $headers[0]);                                          If ( !emptyempty($head[1]) && intval($head[1]) < 400) return true;
                                                                                           return false;                                      }

The example code to exclude redirection is as follows:

Copy code

The code is as follows:

<?php 
/**
* Fetches all the real headers sent by the server in response to a HTTP request without redirects
* Get headers without redirects
​*/ 
    
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; 
} 
?>

希望本文所述对大家的PHP程序设计有所帮助。

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