你可以使用cURL:

<?php
//The url you wish to send the POST request to
$url = $file_name;

//The data you want to send via POST
$fields = [
    '__VIEWSTATE '      => $state,
    '__EVENTVALIDATION' => $valid,
    'btnSubmit'         => 'Submit'
];

//url-ify the data for the POST
$fields_string = http_build_query($fields);

//open connection
$ch = curl_init();

//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL, $url);
curl_setopt($ch,CURLOPT_POST, true);
curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);

//So that curl_exec returns the contents of the cURL; rather than echoing it
curl_setopt($ch,CURLOPT_RETURNTRANSFER, true); 

//execute post
$result = curl_exec($ch);
echo $result;
?>

用PHP发送GET或POST请求的更好方法如下:

<?php
    $r = new HttpRequest('http://example.com/form.php', HttpRequest::METH_POST);
    $r->setOptions(array('cookies' => array('lang' => 'de')));
    $r->addPostFields(array('user' => 'mike', 'pass' => 's3c|r3t'));

    try {
        echo $r->send()->getBody();
    } catch (HttpException $ex) {
        echo $ex;
    }
?>

代码摘自官方文档http://docs.php.net/manual/da/httprequest.send.php

这里只使用了一个没有cURL的命令。超级简单。

echo file_get_contents('https://www.server.com', false, stream_context_create([
    'http' => [
        'method' => 'POST',
        'header'  => "Content-type: application/x-www-form-urlencoded",
        'content' => http_build_query([
            'key1' => 'Hello world!', 'key2' => 'second value'
        ])
    ]
]));

这里有这样的代码:

<?php
$postdata = http_build_query(
    array(
        'name' => 'Robert',
        'id' => '1'
    )
);
$opts = array('http' =>
    array(
        'method' => 'POST',
        'header' => 'Content-type: application/x-www-form-urlencoded',
        'content' => $postdata
    )
);
$context = stream_context_create($opts);
$result = file_get_contents('http://localhost:8000/api/test', false, $context);
echo $result;?>

我使用下面的函数来使用curl发布数据。$data是一个要发布的字段数组(将使用http_build_query()正确编码)。

function httpPost($url, $data)
{
    $curl = curl_init($url);
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($data));
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($curl);
    curl_close($curl);
    return $response;
}

@Edward提到http_build_query()可能被省略，因为curl将正确编码传递给CURLOPT_POSTFIELDS参数的数组，这是正确的，但请注意，在这种情况下，数据将使用multipart/form-data进行编码，这可能不可取，因为一些端点希望数据使用application/x-www-form-urlencoded进行编码。当像上面的函数一样使用http_build_query()时，数据将使用application/x-www-form-urlencoded进行编码。

上面的答案对我不起作用。这是第一个完美运行的解决方案:

$sPD = "name=Jacob&bench=150"; // The POST Data
$aHTTP = array(
  'http' => // The wrapper to be used
    array(
    'method'  => 'POST', // Request Method
    // Request Headers Below
    'header'  => 'Content-type: application/x-www-form-urlencoded',
    'content' => $sPD
  )
);
$context = stream_context_create($aHTTP);
$contents = file_get_contents($sURL, false, $context);

echo $contents;