PHP function grabs remote images to local

//php ob function library to grab remote images
function GetImage($url, $filename = "") {
if ($url == "") {
return false;
}
if ($filename == "") {
$ext = strrchr ( $url, "." );
if ($ext != ".gif" && $ext != ".jpg ") {
return false;
}
$filename = time () . $ext;
}
//File saving path
ob_start ();
readfile ( $url );
 $img = ob_get_contents ();
ob_end_clean ();
$size = strlen ( $img );
//File size
$fp2 = @fopen ( $filename, "a" ) ;
fwrite ( $fp2, $img );
fclose ( $fp2 );
return $filename;
}
GetImage ( "http://XXXXX" );