php使用socket获取远程图片

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：

<?php
/*
 * 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 = "http://su.bdimg.com/static/superplus/img/logo_white.png";
$result = get_remote_picture($url);
if($result){
	echo 'get remote picture success';
}else{
	echo 'get remote picture failed';
}