Mi rispondo....da sola

Codice PHP:

$url 
"http://www.altrosito.net";
$file "10049.pdf";

        
$path "".$url."/documenti/".$file."";
        
        
$getHeaders = @get_headers($path);
        
        if (!
preg_match("|200|"$getHeaders[0])) {
        
            
$x =1;
                    
            while (!
preg_match("|200|"$getHeaders[0])){

                
$path "".$url."/documenti/".$x."/".$file."";
                
                
$getHeaders = @get_headers($path);
                
                
$x++;
                
            }

        }        
echo 
$path