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);
?>