如何验证file_get_contents（）？

I have a file in my site, ex: http://example.com/name.txt

I would like to check if this file exists inside a function, so I did this

<?php

function checkFile($fileUrl){
   if(!is_file($fileUrl) || !is_readable($fileUrl)){
    return 'This is not valid file';
   }

}

Since checkFile('http://example.com/name.txt'); said it could not file the file, I tried to also check using this method.

function checkFile($fileUrl){
       $file = file_get_contents($fileUrl); 
       if(empty){
         return 'File not found or empty';
       }
    }

But both approach are giving me errors static that the file is not found. I am sure the file is there, so how can I actually check if files exists in online?

function checkFile($fileUrl) {
    if (!file_exists($fileUrl)) {
        return 'This file is not a valid file.';
    }
}

Side Note This is only valid as of PHP 5 http://us1.php.net/manual/en/function.file-exists.php

Alternatively you can check response headers from server if 404 then file doesn't exist using function

get_headers()

http://us1.php.net/manual/en/function.get-headers.php

$file = 'http://www.domain.com/somefile.jpg';
$file_headers = @get_headers($file);
if($file_headers[0] == 'HTTP/1.1 404 Not Found') {
    $exists = false;
}
else {
    $exists = true;
}