How to determine whether a remote image file exists in PHP_PHP Tutorial

fopen() method

The easiest way is to use fopen() to see if the file can be opened. If it can be opened, the file will of course exist.

<?php
$url = 'http://www.bkjia.com/images/test.jpg';

if( @fopen( $url, 'r' ) ) 
{ 
	echo 'File Exits';
} 
else 
{
	echo 'File Do Not Exits';
}
?>

fopen() function opens a file or URL. If the open fails, the function returns FALSE.

Syntax: fopen(filename,mode,include_path,context)

Possible values ​​for the mode parameter:

fopen() binds the name resource specified by filename to a stream. If filename is of the form "scheme://...", it is treated as a URL and PHP will search for a protocol handler (also called a wrapper protocol) to handle the scheme. If the wrapper protocol has not been registered for the protocol, PHP will emit a message to help check for potential problems in the script and continue execution of filename as if it were a normal filename.

If PHP thinks filename specifies a local file, it will try to open a stream on that file. The file must be accessible to PHP, so you need to confirm that the file access permissions allow this access. If safe mode or open_basedir is activated further restrictions apply.

If PHP believes that filename specifies a registered protocol, and the protocol is registered as a network URL, PHP will check and confirm that allow_url_fopen has been activated. If it is closed, PHP will issue a warning and the call to fopen will fail.

Usage of fopen

<?php
$file = fopen("test.txt","r");
$file = fopen("/home/test/test.txt","r");
$file = fopen("/home/test/test.gif","wb");
$file = fopen("http://www.example.com/","r");
$file = fopen("ftp://user:password@example.com/test.txt","w");
?>

But if the server where the image resource is located hangs up, this function will wait forever, so we need a backup plan.

CURL method

CURL is a very useful class library. Let’s see how to use it to judge.

<?php
$url2 = 'http://www.bkjia.com/test.jpg';

$ch = curl_init(); 
$timeout = 10; 
curl_setopt ($ch, CURLOPT_URL, $url2); 
curl_setopt($ch, CURLOPT_HEADER, 1); 
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, $timeout); 

$contents = curl_exec($ch);
//echo $contents;
if (preg_match("/404/", $contents)){
	echo '文件不存在';
}
?>

If the file does not exist after curl_exec() is executed, the following information will be returned:

HTTP/1.1 404 Not Found
Date: Tue, 14 Feb 2012 05:08:34 GMT
Server: Apache
Accept-Ranges: bytes
Content-Length: 354
Content-Type: text/html

Use regular expressions to see if there is a 404. If so, the file does not exist.