<?php
$login = $_POST['log'];
$password = $_POST['pas'];
if($login == 'login' && $password == 'password' && !empty($login) && !empty($password)) 
{ 
    echo "Успешная авторизация";
} 
else 
{
    echo "Логин или пароль не верные" ;
}
?>

HINTERNET hRequest;
static TCHAR hdrs[] =
TEXT("Content-Type: application/x-www-form-urlencoded");
static TCHAR accept[] = "Accept: *|*"; 
char data[1024];
strcpy(data,"log=login&pas=password");
HINTERNET hSession = (0,1, INTERNET_OPEN_TYPE_PROXY, _T("site.com"), 0, 0,
INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);			
if(hSession!=NULL)
{
	HINTERNET hConnect = InternetConnect(hSession, SERVERNAME,
	INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
	if(hConnect!=NULL)
	{
		hRequest = HttpOpenRequest(hConnect, TEXT("POST"),
                "login.php", NULL, NULL,(const char **) &accept, INTERNET_FLAG_KEEP_CONNECTION, 1);
		if(hRequest!=NULL) 
		{
			if(!HttpSendRequest(hRequest, hdrs, -1L, data, strlen(data))) 
			{
				MessageBox(NULL,"Подключитесь к интернету","Error",MB_OK); 
			}                
			
		}
		InternetCloseHandle(hRequest); 
	}
	InternetCloseHandle(hConnect); 
InternetCloseHandle(hSession);
}