<?php
set_time_limit(0);


$url_for_login_page = 'http://site.com/login.php';
$url = 'http://site.com/';

# все значение из формы для логина
$post_data = 'login=mylogin&pass=mypass&tralala=1';

$curl = curl_init ( );

curl_setopt ( $curl, CURLOPT_URL, $url_for_login_page );
curl_setopt ( $curl, CURLOPT_FOLLOWLOCATION, 1 );

curl_setopt ( $curl, CURLOPT_POST, 1 );
curl_setopt ( $curl, CURLOPT_POSTFIELDS, $post_data );

curl_setopt ( $curl, CURLOPT_COOKIESESSION, 1 );
curl_setopt ( $curl, CURLOPT_COOKIEJAR, 'cookie.txt' );
curl_setopt ( $curl, CURLOPT_COOKIEFILE, 'cookie.txt' );

curl_setopt ( $curl, CURLOPT_TIMEOUT, 5 );

curl_exec ( $curl );
  
while ( 1 )
{
  
  curl_setopt ( $curl, CURLOPT_URL, $url );

  curl_setopt ( $curl, CURLOPT_COOKIESESSION, 1 );
  curl_setopt ( $curl, CURLOPT_COOKIEJAR, 'cookie.txt' );
  curl_setopt ( $curl, CURLOPT_COOKIEFILE, 'cookie.txt' );

  curl_setopt ( $curl, CURLOPT_TIMEOUT, 5 );

  curl_exec ( $curl );

  sleep ( 30 );

}
?>