About data transfer CURL in PHP

[root@fengniu020 ~]# php -i | grep -i curl
Additional .ini files parsed => /etc/php.d/curl.ini,
curl
cURL support => enabled
cURL Information => 7.19.7

<?php
$curl=curl_init(&#39;//www.jb51.net&#39;);
curl_exec($curl);
curl_close($curl);
?>

<?php
/**
 * 实例描述：在网络上下载一个网页并把内容中的“百度”替换为“摆渡”之后输出
 */
$curlobj = curl_init();      // 初始化
curl_setopt($curlobj, CURLOPT_URL, "http://www.baidu.com");    // 设置访问网页的URL
curl_setopt($curlobj, CURLOPT_RETURNTRANSFER, true);      // 执行之后不直接打印出来
$output=curl_exec($curlobj); // 执行
curl_close($curlobj);     // 关闭cURL
echo str_replace("百度","摆渡",$output);
?>

<?php
/**
 * 实例描述：通过调用WebService查询北京的当前天气
 * 下方接口，免费用户24小时内访问是有限制的，需要存储信息
 */
$data = &#39;theCityName=北京&#39;;
//$data = &#39;theCityName=北京&&#39;;//多个用&号连接
$curlobj = curl_init();  
curl_setopt($curlobj, CURLOPT_URL, "http://www.webxml.com.cn/WebServices/WeatherWebService.asmx/getWeatherbyCityName"); 
curl_setopt($curlobj, CURLOPT_HEADER, 0); 
curl_setopt($curlobj, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($curlobj, CURLOPT_POST, 1); //POST方式
curl_setopt($curlobj, CURLOPT_POSTFIELDS, $data); 
curl_setopt($curlobj, CURLOPT_HTTPHEADER, array("application/x-www-form-urlencoded; charset=utf-8", 
  "Content-length: ".strlen($data)
  )); //HTTP请求头
curl_setopt ($curlobj, CURLOPT_USERAGENT, $_SERVER[&#39;HTTP_USER_AGENT&#39;]);
$rtn = curl_exec($curlobj);  
if(!curl_errno($curlobj)){
  // $info = curl_getinfo($curlobj); 
  // print_r($info);
  echo $rtn; 
} else {
 echo &#39;Curl error: &#39; . curl_error($curlobj);
}
curl_close($curlobj);
?>

<?php
/**
 * 代码实例-PHP-cURL实战
 * 实例描述：从FTP服务器下载一个文件到本地
 */
$curlobj = curl_init();  
curl_setopt($curlobj, CURLOPT_URL, "ftp://192.168.1.100/downloaddemo.txt"); 
curl_setopt($curlobj, CURLOPT_HEADER, 0); 
curl_setopt($curlobj, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($curlobj, CURLOPT_TIMEOUT, 300); // times out after 300s
curl_setopt($curlobj, CURLOPT_USERPWD, "peter.zhou:123456");//FTP用户名：密码
// Sets up the output file
$outfile = fopen(&#39;dest.txt&#39;, &#39;wb&#39;);//保存到本地的文件名
curl_setopt($curlobj, CURLOPT_FILE, $outfile);

$rtn = curl_exec($curlobj); 
fclose($outfile); 
if(!curl_errno($curlobj)){
  // $info = curl_getinfo($curlobj); 
  // print_r($info);
  echo "RETURN: " . $rtn; 
} else {
 echo &#39;Curl error: &#39; . curl_error($curlobj);
}
curl_close($curlobj);
?>

<?php
/**
 * 代码实例-PHP-cURL实战
 * 实例描述：把本地文件上传到FTP服务器上
 */
$curlobj = curl_init();  
$localfile = &#39;ftp01.php&#39;;//需要上传的文件
$fp = fopen($localfile, &#39;r&#39;);

curl_setopt($curlobj, CURLOPT_URL, "ftp://192.168.1.100/ftp01_uploaded.php");//上传后保存的文件名
curl_setopt($curlobj, CURLOPT_HEADER, 0); 
curl_setopt($curlobj, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($curlobj, CURLOPT_TIMEOUT, 300); // times out after 300s
curl_setopt($curlobj, CURLOPT_USERPWD, "peter.zhou:123456");//FTP用户名：密码

curl_setopt($curlobj, CURLOPT_UPLOAD, 1);
curl_setopt($curlobj, CURLOPT_INFILE, $fp);//传输打开的文件
curl_setopt($curlobj, CURLOPT_INFILESIZE, filesize($localfile));//上传的文件大小
$rtn = curl_exec($curlobj); 
fclose($fp); 
if(!curl_errno($curlobj)){
  echo "Uploaded successfully."; 
} else {
 echo &#39;Curl error: &#39; . curl_error($curlobj);
}
curl_close($curlobj);
?>

<?php
/**
 * 代码实例-PHP-cURL实战
 * 实例描述：下载网络上面的一个HTTPS的资源
 */
$curlobj = curl_init();      // 初始化
curl_setopt($curlobj, CURLOPT_URL, "https://ajax.aspnetcdn.com/ajax/jquery.validate/1.12.0/jquery.validate.js");    // 设置访问网页的URL
curl_setopt($curlobj, CURLOPT_RETURNTRANSFER, true);      // 执行之后不直接打印出来

// 设置HTTPS支持
date_default_timezone_set(&#39;PRC&#39;); // 使用Cookie时，必须先设置时区
curl_setopt($curlobj, CURLOPT_SSL_VERIFYPEER, 0); // 对认证证书来源的检查从证书中检查SSL加密算法是否存在,设置为0就是终止从服务器端进行验证
curl_setopt($curlobj, CURLOPT_SSL_VERIFYHOST, 2); // 

$output=curl_exec($curlobj); // 执行
curl_close($curlobj);     // 关闭cURL
echo $output;
?>