步骤：
1，匹配URL中的主机名和文件部分
2，创建socket并连接到目标服务器
3，构造HTTP请求并发送
4，读取HTTP响应并解析
5，保存内容到文件并关闭socket连接
代码实现如下：
/*
* 使用socket获取远程资源(网页，图片等)
* url 资源URL
* savepath 资源的保存路径
* return true/false
*/
function get_remote_picture($url,$savepath="./"){
set_time_limit(0);
$pattern = '/(http:\/\/)?([^\/]+)(.+)/';
$res = preg_match($pattern, $url, $matches);
if($res == 0){
return false;
}
$host = "";//主机名
$file = "";//请求的文件
if(count($matches) == 3){
$host = $matches[1];
$file = $matches[2];
}else if(count($matches) == 4){
$host = $matches[2];
$file = $matches[3];
}else{
return false;
}
$socket = socket_create(AF_INET,SOCK_STREAM,SOL_TCP);
$res = socket_connect($socket,gethostbyname($host),80);
if(!$res){
//echo socket_strerror(socket_last_error($socket));
socket_close($socket);
return false;
}
$request = "";
$request .= "GET $file HTTP/1.1\r\n";
$request .= "Host: $host\r\n";
$request .= "Connection: close\r\n\r\n";
$len = socket_write($socket,$request);
$response = "";
while($buf=socket_read($socket,512)){
if(strlen($buf) == 0){
break;
}
$response .= $buf;
}
if(strpos($response,"\r\n\r\n")){
$arr = explode("\r\n\r\n",$response);
if(!file_exists($savepath)){
@mkdir($savepath);
}
$savepath = rtrim($savepath,'/').'/';
file_put_contents($savepath.basename($file),$arr[1]);
}else{
socket_close($socket);
return false;
}
socket_close($socket);
return true;
}
/* 获取百度logo */
$url = "/static/superplus/img/logo_white.png";
$result = get_remote_picture($url);
if($result){
echo 'get remote picture success';
}else{
echo 'get remote picture failed';
}
