检查URL是否为zip格式

我根据这个答案改编了我的代码，改为从响应中读取4个字节(使用Range，或者在读取4个字节后中止)，然后查看4个字节是否与zip魔术头匹配。

试一试，让我知道结果。您可能需要添加一些错误检查，以查看curl请求是否由于某种原因失败而无法确定文件类型。

<?php
/**
 * Try to determine if a remote file is a zip by making an HTTP request for
 * a byte range or aborting the transfer after reading 4 bytes.
 *
 * @return bool true if the remote file is a zip, false otherwise
 */
function isRemoteFileZip($url)
{
    $ch = curl_init($url);
    $headers = array(
        'Range: bytes=0-4',
        'Connection: close',
    );
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2450.0 Iron/46.0.2450.0');
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
    curl_setopt($ch, CURLOPT_VERBOSE, 0); // set to 1 to debug
    curl_setopt($ch, CURLOPT_STDERR, fopen('php://output', 'r'));
    $header = '';
    // write function that receives data from the response
    // aborts the transfer after reading 4 bytes of data
    curl_setopt($ch, CURLOPT_WRITEFUNCTION, function($curl, $data) use(&$header) {
        $header .= $data;
        if (strlen($header) < 4) return strlen($data);
        return 0; // abort transfer
    });
    $result = curl_exec($ch);
    $info   = curl_getinfo($ch);
    // check for the zip magic header, return true if match, false otherwise
    return preg_match('/^PK(?:'x03'x04|'x05'x06|0x07'x08)/', $header);
}
var_dump(isRemoteFileZip('https://example.com/file.zip'));
var_dump(isRemoteFileZip('https://example.com/logo.png'));