<?php
   if (!function_exists('session_regenerate_id')) {
       function php_combined_lcg() {
           $tv = gettimeofday();
           $lcg['s1'] = $tv['sec'] ^ (~$tv['usec']);
           $lcg['s2'] = posix_getpid();

           $q = (int) ($lcg['s1'] / 53668);
           $lcg['s1'] = (int) (40014 * ($lcg['s1'] - 53668 * $q) - 12211 * $q);
           if ($lcg['s1'] < 0)
               $lcg['s1'] += 2147483563;

           $q = (int) ($lcg['s2'] / 52774);
           $lcg['s2'] = (int) (40692 * ($lcg['s2'] - 52774 * $q) - 3791 * $q);
           if ($lcg['s2'] < 0)
               $lcg['s2'] += 2147483399;

           $z = (int) ($lcg['s1'] - $lcg['s2']);
           if ($z < 1) {
               $z += 2147483562;
           }

           return $z * 4.656613e-10;
       }

       function session_regenerate_id() {
           $tv = gettimeofday();
           $buf = sprintf("%.15s%ld%ld%0.8f", $_SERVER['REMOTE_ADDR'], $tv['sec'], $tv['usec'], php_combined_lcg() * 10);
           session_id(md5($buf));
           if (ini_get('session.use_cookies'))
               setcookie('PHPSESSID', session_id(), NULL, '/');
           return TRUE;
       }
   }
?>

<?php
   session_start();
   $sid = session_id();
   session_regenerate_id();
   echo "Old session ID: ", $sid, "\nNew session ID: ", session_id(), "\n";
?>

<?php delete_from_file('linea a borrar'); ?>

<?php

$textfile = "keys.txt";

function delete_from_file($key) {

global $textfile;
$newline = 'used:'.$key.'';
$handle = fopen($textfile, "r");

while(!feof($handle))  {

$line = fgets($handle, 1024);
$file = eregi($key,$line);
if ($file) {
if(!empty($line)){
$data=file($textfile);
$size=count($data); 
$fp = fopen($textfile, "w");
for ($n=0; $n < $size; $n++) {
if ($data[$n] != $key) {
fputs($fp , $data[$n]);
}
}
}
}
}

}?>