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Homephp教程php手册PHP判断远程图片是否存在的几种方法

在做一个图片预览中图的东西,遇到一个问题,就是要判断远程文件是否存在(不是同一台服务器)。
代码如下:

复制代码 代码如下:


//方法一
function file_exists($url)
{
$ch = curl_init();
curl_setopt($ch, curlopt_url,$url);
curl_setopt($ch, curlopt_nobody, 1); // 不下载
curl_setopt($ch, curlopt_failonerror, 1);
curl_setopt($ch, curlopt_returntransfer, 1);

if(curl_exec($ch)!==false)
return true;
else
return false;
}

//方法二
function file_exists2($url)
{
if(file_get_contents($url,0,null,0,1))
return 1;
else
return 0;
}
//方法三
function file_exists($url) {
$curl = curl_init($url);
// 不取回数据
curl_setopt($curl, CURLOPT_NOBODY, true);
// 发送请求
$result = curl_exec($curl);
$found = false;
// 如果请求没有发送失败
if ($result !== false) {
// 再检查http响应码是否为200
}

方法一无论图片在不在都是返回FALSE;
方法二windows下可行,LINUX下无论图片在不在都返加TRUE;
方法三应该是最合适的
另外:用get_headers() 方法存在效率问题,建议不使用作为此解决方案

fsockopen版:

复制代码 代码如下:


  $url = "http://www.baidu.com/img/baidu_sylogo1.gif";

    $info = parse_url($url);
    $fp = fsockopen($info['host'], 80,$errno, $errstr, 30);
    fputs($fp,"GET {$info['path']} HTTP/1.1\r\n");
    fputs($fp, "Host: {$info['host']}\r\n");
    fputs($fp, "Connection: close\r\n\r\n");
    $headers = array();
    while(!feof($fp)) {
    $line = fgets($fp);
    if($line != "\r\n") {
    $headers[] = $line;
    }else {
    break;
    }
    }

    echo "

";<br>    print_r($headers);<br>
<p>通过http状态码来判断文件是否存在,比如,响应 302,301,404等都为不存在,如果是200,304,等可以视为文件存在。</p>
<p>fopen()方法:<br></p><p class="codetitle"><span style="CURSOR: pointer" onclick="doCopy('code37338')"><u>复制代码</u></span> 代码如下:</p><p class="code" id="code37338"><br><?php <BR>    $url = 'http://www.test.com/images/test.jpg';<br><br>    if( @fopen( $url, 'r' ) )<br>    {<br>        echo 'File Exits';<br>    }<br>    else<br>    {<br>        echo 'File Do Not Exits';<br>    }<br>    ?><br></p><br>CURL方法:<br><p class="codetitle"><span style="CURSOR: pointer" onclick="doCopy('code76859')"><u>复制代码</u></span> 代码如下:</p><p class="code" id="code76859"><br><?php <BR>    $url2 = 'http://www.test.com/test.jpg';<br><br>    $ch = curl_init();<br>    $timeout = 10;<br>    curl_setopt ($ch, CURLOPT_URL, $url2);<br>    curl_setopt($ch, CURLOPT_HEADER, 1);<br>    curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);<br>    curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, $timeout);<br><br>    $contents = curl_exec($ch);<br>    //echo $contents;<br>    if (preg_match("/404/", $contents)){<br>        echo '文件不存在';<br>    }<br>    ?><br></p>

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