how to generate random non repeated numbers in php

Hi all. could an expert show me how i can generate random non repeated numbers. I want to use those number as file name that i write to. currently the file name is ram.txt but i want it the file name to be like 948450913.txt each time the scripts runs diffrent number .I be happy if an expert show me how to do that here in this code?thanks

Code:

---

<?php


$url[1] = "http://localhost/flash_mp3_player/mp3/08 - Track 8.mp3";
$url[2] = "http://localhost/flash_mp3_player/mp3/13 - Gar Aya.mp3";
$url[3] = "http://localhost/flash_mp3_player/mp3/Soroush - Yeh Donya - 02 Shoghe Nafas.mp3";

$mycontent = "";
if (isset($_GET["sid"]))
{
  $allsid = explode (",",$_GET["sid"]);
  $mycontent = array();
  foreach ($allsid AS $value)
      $mycontent[] = $url[$value];
}

echo $mycontent;

$handle = fopen ("ram.txt","w+");
if ($handle)
{
  if (fwrite ( $handle,implode("\r\n",$mycontent)."\r\n") )
  {
      echo "FILE IS WRITTEN SUCCESSFULLY";
  } else
  {
      echo "ERROR IN WRITING TO FILE";
  }
  fclose ($handle);
} else
{
      echo "ERROR IN OPENING FILE";
}
require 'config.txt';
?>

---

Difficult, very difficult to do perfectly. (Or memory-intensive.)

Realistically, though, if you just use uniqid() to generate an ID, the collision probability is so low that you can just form the filename, check if it exists, and if it does, request a new ID. Repeat until you find a free slot. It really shouldn't take more than two tries, three at the very most, and only if you're particularly unlucky and have a LOT of files already stored.

You could use the time that it was generated on by using time() (http://uk2.php.net/manual/en/function.time.php)

PHP Code:

---

$filename = time() . ".txt";
$handle = fopen ($filename,"w+"); 


---

This might prove to have too little resolution: two requests within a second would attempt to open the same file.

Quote:

---

Originally Posted by john tindell

You could use the time that it was generated on by using time() (http://uk2.php.net/manual/en/function.time.php)

PHP Code:

---

$filename = time() . ".txt";
$handle = fopen ($filename,"w+"); 


---

---

many thanks for u reply. the whole idea of doing this is to generate unique file for each request from user .Do think by using this method no 2 user get same .txt file when they execute this page?Thanks