规定时间内，生产随机数不变rand()

@session_start();
$currentTime = time();
$changeTime = 10;
$rand = '';
if(isset($_SESSION['time'])) {
if(($currentTime - $_SESSION['time']) >= $changeTime) {
$_SESSION['time'] = $currentTime;
$rand = (0, 9999);
$_SESSION['rand'] = $rand;
}else{
$rand = $_SESSION['rand'];
}
}else{
$_SESSION['time'] = $currentTime;
$rand = (0, 9999);
$_SESSION['rand'] = $rand;
}

<?php
session_start();
function _rand($_i){
$currentTime = time();
$changeTime = 10;
$rand = '';
if(isset($_SESSION['time'][$_i])){
if(($currentTime - $_SESSION['time'][$_i]) >= $changeTime) {
switch ($_i){
case '0':
$_SESSION['rand'][$_i] = mt_rand(100,200);
$rand = $_SESSION['rand'][$_i];
break;
case '1':
$_SESSION['rand'][$_i] = mt_rand(200,300);
$rand = $_SESSION['rand'][$_i];
break;
case '2':
$_SESSION['rand'][$_i] = mt_rand(300,400);
$rand = $_SESSION['rand'][$_i];
break;
}
$_SESSION['time'][$_i] = $currentTime;
}else{
switch ($_i){
case '0':
$rand = $_SESSION['rand'][$_i];
break;
case '1':
$rand = $_SESSION['rand'][$_i];
break;
case '2':
$rand = $_SESSION['rand'][$_i];
break;
}
}

}else{
if(!isset($_SESSION['time'])){
$_SESSION['time'] = array();
}
switch ($_i){
case '0':
$_SESSION['rand'][$_i] = mt_rand(100,200);
$rand = $_SESSION['rand'][$_i];
break;
case '1':
$_SESSION['rand'][$_i] = mt_rand(200,300);
$rand = $_SESSION['rand'][$_i];
break;
case '2':
$_SESSION['rand'][$_i] = mt_rand(300,400);
$rand = $_SESSION['rand'][$_i];
break;
}
$_SESSION['time'][$_i] = $currentTime;
}

return $rand;
}

?>

<div >
<i><?php  echo _rand(0) ;?></i><b>|</b>
<i><?php  echo _rand(1) ;?></i><b>|</b>
<i><?php  echo _rand(2) ;?></i><b>|</b>
</div>