PHP中 fsockopen 函数怎么用？

<?php
$fp = fsockopen("www.example.com", 80, $errno, $errstr, 30);
if (!$fp) {
    echo "$errstr ($errno)<br />\n";
} else {
    $out = "GET / HTTP/1.1\r\n";
    $out .= "Host: www.example.com\r\n";
    $out .= "Connection: Close\r\n\r\n";
    fwrite($fp, $out);
    while (!feof($fp)) {
        echo fgets($fp, 128);
    }
    fclose($fp);
}
?>

<?php
$fp = fsockopen("udp://127.0.0.1", 13, $errno, $errstr);
if (!$fp) {
    echo "ERROR: $errno - $errstr<br />\n";
} else {
    fwrite($fp, "\n");
    echo fread($fp, 26);
    fclose($fp);
}
?>

<?php
$host = "something.example.com";
$port = 443;
$path = "/the/url/path/file.php"; //or .dll, etc. for authnet, etc.

//you will need to setup an array of fields to post with
//then create the post string
$formdata = array ( "x_field" => "somevalue");
//build the post string
  foreach($formdata AS $key => $val){
    $poststring .= urlencode($key) . "=" . urlencode($val) . "&";
  }
// strip off trailing ampersand
$poststring = substr($poststring, 0, -1);

$fp = fsockopen("ssl://".$host, $port, $errno, $errstr, $timeout = 30);

if(!$fp){
//error tell us
echo "$errstr ($errno)\n";
  
}else{

  //send the server request
  fputs($fp, "POST $path HTTP/1.1\r\n");
  fputs($fp, "Host: $host\r\n");
  fputs($fp, "Content-type: application/x-www-form-urlencoded\r\n");
  fputs($fp, "Content-length: ".strlen($poststring)."\r\n");
  fputs($fp, "Connection: close\r\n\r\n");
  fputs($fp, $poststring . "\r\n\r\n");

  //loop through the response from the server
  while(!feof($fp)) {
    echo fgets($fp, 4096);
  }
  //close fp - we are done with it
  fclose($fp);
}