php 判断远路图片是否有效

	$url = "http://www.iteye.com/upload/logo/user/275746/46a4c886-427e-3554-b195-083430beb92a.jpg";	echo "<a href='$url'>$url</a><br/>";	$arr = get_headers($url,1);	echo $arr["Content-Type"]; //image/jpeg

$url = 'http://www.example.com';print_r(get_headers($url));print_r(get_headers($url, 1));?> 上例的输出类似于：Array(    [0] => HTTP/1.1 200 OK    [1] => Date: Sat, 29 May 2004 12:28:13 GMT    [2] => Server: Apache/1.3.27 (Unix)  (Red-Hat/Linux)    [3] => Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT    [4] => ETag: "3f80f-1b6-3e1cb03b"    [5] => Accept-Ranges: bytes    [6] => Content-Length: 438    [7] => Connection: close    [8] => Content-Type: text/html)Array(    [0] => HTTP/1.1 200 OK    [Date] => Sat, 29 May 2004 12:28:14 GMT    [Server] => Apache/1.3.27 (Unix)  (Red-Hat/Linux)    [Last-Modified] => Wed, 08 Jan 2003 23:11:55 GMT    [ETag] => "3f80f-1b6-3e1cb03b"    [Accept-Ranges] => bytes    [Content-Length] => 438    [Connection] => close    [Content-Type] => text/html)