how to check if a link exists

for example how would I check whether an image URL exists or not?
ie: http://someone-elses-site.com/flower.gif
??

saw this function somewhere - cant vouch for it but it seems to work.
i.e

if (remote_file_exists('where.ever.com')){
// yes
}
---------------------------------------------------
function remote_file_exists($url)
{
$head = '';
$url_p = parse_url ($url);

if (isset ($url_p['host']))
{ $host = $url_p['host']; }
else
{
return '1 Invalid URL host';
}

if (isset ($url_p['path']))
{ $path = $url_p['path']; }
else
{ $path = ''; }

$fp = fsockopen ($host, 80, $errno, $errstr, 20);
if (!$fp)
{
return '2 Unable to connect to remote host';
}
else
{
$parse = parse_url($url);
$host = $parse['host'];

fputs($fp, 'HEAD '.$url." HTTP/1.1\r\n");
fputs($fp, 'HOST: '.$host."\r\n");
fputs($fp, "Connection: close\r\n\r\n");
$headers = '';
while (!feof ($fp))
{ $headers .= fgets ($fp, 128); }
}
fclose ($fp);

// for debug
//echo nl2br($headers);

$arr_headers = explode("\n", $headers);
if (isset ($arr_headers[0])) {
if(strpos ($arr_headers[0], '200') !== false)
{ return true; }
if( (strpos ($arr_headers[0], '404') !== false) ||
(strpos ($arr_headers[0], '410') !== false))
{ return false; }
if( (strpos ($arr_headers[0], '301') !== false) ||
(strpos ($arr_headers[0], '302') !== false))
{
preg_match("/Location:\s*(.+)\r/i", $headers, $matches);
if(!isset($matches[1]))
return false;
$nextloc = $matches[1];
return remote_file_exists($nextloc);
}
}
preg_match('/HTTP.*(\d\d\d.*)\r/i', $headers, $matches);
return '3 Status Code not supported'.
(isset($matches[1])?": $matches[1]":'');
}

thanks, but that method didn't work for me
I ended up using a check for @getimagesize(), which worked pretty well.