php判断文件是否存在，可使用如下代码：
发卡宝-卡密寄售系统
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发卡宝是一个专业的软件卡密等虚拟商品在线交易平台,拥有多种兑换方式,费率低,结算快,正规企业平台一直稳定运营,24小时不间断提供自动发卡服务。【模板说明】试用版自带一套模板（响应式）【环境支持】PHP环境 / 200M或以上空间大小 / 开启父路径 / 设置index.php为默认首页 / 目录写入权限需要开启【数据库】MySQL【安装步骤】将文件上传至空间目录，运行“http://域名/inst
<ol class="dp-c"><li class="alt"><span><span class="comment">//判断远程文件是否存在 </span><span> </span></span></li><li><span class="keyword">function</span><span> remote_file_exists(</span><span class="vars">$url</span><span>) { </span></li><li class="alt"><span> </span><span class="vars">$executeTime</span><span> = </span><span class="func">ini_get</span><span>(</span><span class="string">'max_execution_time'</span><span>); </span></li><li><span> </span><span class="func">ini_set</span><span>(</span><span class="string">'max_execution_time'</span><span>, 0); </span></li><li class="alt"><span> </span><span class="vars">$headers</span><span> = @get_headers(</span><span class="vars">$url</span><span>); </span></li><li><span> </span><span class="func">ini_set</span><span>(</span><span class="string">'max_execution_time'</span><span>, </span><span class="vars">$executeTime</span><span>); </span></li><li class="alt"><span> </span><span class="keyword">if</span><span> (</span><span class="vars">$headers</span><span>) { </span></li><li><span> </span><span class="vars">$head</span><span> = </span><span class="func">explode</span><span>(</span><span class="string">' '</span><span>, </span><span class="vars">$headers</span><span>[0]); </span></li><li class="alt"><span> </span><span class="keyword">if</span><span> (!</span><span class="func">empty</span><span class="keyword">empty</span><span>(</span><span class="vars">$head</span><span>[1]) && </span><span class="func">intval</span><span>(</span><span class="vars">$head</span><span>[1]) < 400) </span><span class="keyword">return</span><span> true; </span></li><li><span> } </span></li><li class="alt"><span> </span><span class="keyword">return</span><span> false; </span></li><li><span>} </span></li></ol>
