HTTP Post request to a PHP server

 integer SECRET_NUMBER=123456789;
 
 xrequest(string url, list l)
 {
     integer i;
     integer len=llGetListLength(l) & 0xFFFE; // makes the list count even
     string body;
 
    for (i=0;i<len;i+=2)
    {
         string varname=llList2String(l,i);
         string varvalue=llList2String(l,i + 1);
         if (i>0) body+="&";
         body+=llEscapeURL(varname)+"="+llEscapeURL(varvalue);
     }
     string hash=llMD5String(body,SECRET_NUMBER);
     http_request_id = llHTTPRequest(url+"?hash="+hash,[HTTP_METHOD,"POST",HTTP_MIMETYPE,"application/x-www-form-urlencoded"],body);
 }

On the server side here is the PHP function which will allow your server to check the security hash:

  <?php
  // this function tweak slightly urlencode to make it behave exactly like llEscapeURL in Second Life.
  function llEscapeURL($s)
  {
  	return str_replace(
  		array("+","-",".","_"),
  		array("%20","%2D","%2E","%5F"),
  		urlencode($s));
  }   
  
  // this my main SL page XML-RPC page
  function checkHash()
  {
  	global $body;
  	$hash=$_GET["hash"];
  	$body="";
  	$cpt=0;
  	$SECRET_NUMBER=123456789;
  	foreach ($_POST as $name => $value) {
  		if ($cpt++>0) $body.="&";
  		$body.=llEscapeURL($name)."=".llEscapeURL($value);
  	}
  	$calcHash=md5($body.':'.$SECRET_NUMBER);
  	if ($hash!=$calcHash) 
  	{
  		sleep(2); // slow down the requests
  		echo "result=FAIL\nMSG=Invalid hash"; + $body=""; 
  		die;
  	}
  }
  
  
  checkHash();
  // You can use the parameters here by simply using $_POST["parameter_name"] 
  echo "OK";
  ?>