用这个可以来验证用户和生成随机密码--teaman
<?
  //----------------------------------------------------
  // Function GetSID()
  //
  // Parameters : $nSize number of caracters, default 24
  // Return value : 24 caracters string
  //
  // Description : This function returns a random string
  // of 24 caracters that can be used to identify users
  // on your web site in a more secure way. You can also  
  // use this function to generate passwords.
  //----------------------------------------------------
  function GetSID ($nSize=24) {
 
// Randomize
mt_srand ((double) microtime() * 1000000);
for ($i=1; $i<=$nSize; $i++) {
  
 // if you wish to add numbers in your string,  
 // uncomment the two lines that are commented
 // in the if statement
 $nRandom = mt_rand(1,30);
 if ($nRandom <= 10) {
  // Uppercase letters
  $sessionID .= chr(mt_rand(65,90));
// } elseif ($nRandom <= 20) {
//  $sessionID .= mt_rand(0,9);
 } else {
  // Lowercase letters
  $sessionID .= chr(mt_rand(97,122));
 }
  
}
return $sessionID;
  }
  // Test the function  
  echo GetSID(16);
 ?>