PHP stream_context_create()作用和用法分析

作用：创建并返回一个文本数据流并应用各种选项，可用于fopen(),file_get_contents()等过程的超时设置、代理服务器、请求方式、头信息设置的特殊过程。
函数原型：resource stream_context_create ([ array $options [, array $params ]] )
用法
例子一：

<?php
$opts = array( 'http-->array(
'method'=>"get",
'header'=>"accept-language: en\r\n" .
"cookie: foo=bar\r\n"
)
);
$context = stream_context_create($opts);
/* sends an http request to www.jb51.net
with additional headers shown above */
$fp = fopen('//www.jb51.net', 'r', false, $context);
fpassthru($fp);
fclose($fp);
?>

例子二：

<?php
$opts = array( 'http-->array(
'method'=>"get",
'header'=>"accept-language: en\r\n" .
"cookie: foo=bar\r\n"
)
);
$context = stream_context_create($opts);
?>
you would setup the header this way:
<?php
$opts = array( 'http-->array(
'method'=>"get",
'header'=>array("accept-language: en",
"cookie: foo=bar",
"custom-header: value")
)
);
$context = stream_context_create($opts);
?>

例子三：

<?php
$opts = array('http' => array('proxy' => 'tcp://127.0.0.1:8080', 'request_fulluri' => true));
$context = stream_context_create($opts);
$data = file_get_contents('//www.jb51.net', false, $context);
echo $data;
?>

例子四：

<?php
function do_post_request($url, $postdata, $files = null)
{
$data = "";
$boundary = "---------------------".substr(md5(rand(0,32000)), 0, 10);
//collect postdata
foreach($postdata as $key => $val)
{
$data .= "--$boundary\n";
$data .= "content-disposition: form-data; name=\"".$key."\"\n\n".$val."\n";
}
$data .= "--$boundary\n";
//collect filedata
foreach($files as $key => $file)
{
$filecontents = file_get_contents($file['tmp_name']);
$data .= "content-disposition: form-data; name=\"{$key}\"; filename=\"{$file['name']}\"\n";
$data .= "content-type: image/jpeg\n";
$data .= "content-transfer-encoding: binary\n\n";
$data .= $filecontents."\n";
$data .= "--$boundary--\n";
}
$params = array('http' => array(
'method' => 'post',
'header' => 'content-type: multipart/form-data; boundary='.$boundary,
'content' => $data
));
$ctx = stream_context_create($params);
$fp = fopen($url, 'rb', false, $ctx);
if (!$fp) {
throw new exception("problem with $url, $php_errormsg");
}
$response = @stream_get_contents($fp);
if ($response === false) {
throw new exception("problem reading data from $url, $php_errormsg");
}
return $response;
}
//set data (in this example from post)
//sample data
$postdata = array(
'name' => $_post['name'],
'age' => $_post['age'],
'sex' => $_post['sex']
);
//sample image
$files['image'] = $_files['image'];
do_post_request("//www.jb51.net", $postdata, $files);
?>