php判断远程图片或文件是否存在

function url_exists($url) {$ch = curl_init(); 
    curl_setopt ($ch, CURLOPT_URL, $url); 
    // 不下载
    curl_setopt($ch, CURLOPT_NOBODY, 1);
    // 设置超时
    curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, 3); 
    curl_setopt($ch, CURLOPT_TIMEOUT, 3);
    curl_exec($ch);
    $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);  
    if($http_code == 200) {return true;}
    return false;
}

$url = 'http://www.phpddt.com/img/qrcode_for_phpddt.JPG';
if(@fopen($url, 'r')) {echo '文件存在';} else {echo '文件不存在';}

$url = 'http://www.phpddt.com/img/qrcode_for_phpddt.JPG';
 
stream_context_set_default(
    array(
        'http' => array('timeout' => 1,)
    )
);
 
$headers = get_headers($url);
 
if(preg_match('/200/',$headers[0])) {echo '文件存在';} else {echo '文件不存在';}

$opts = array(
    'http'=>array('timeout'=>3,)
);
$context = stream_context_create($opts);
$resource = @file_get_contents('http://www.phpddt.com/img/qrcode_for_phpddt.JPG', false, $context);
 
if($resource) {echo '文件存在';} else {echo '文件不存在';}