How to generate random numbers in php

<?php
$arr=range(1,10);
shuffle($arr);
foreach($arr as $values)
{
 echo $values." ";
}
?>

<?php
$arr=array();
while(count($arr)<10)
{
 $arr[]=rand(1,10);
 $arr=array_unique($arr);
}
echo implode(" ",$arr);
?>

<?php
$arr=array();
$count1=0;
$count = 0;
$return = array();
while ($count < 10) 
 {
 $return[] = mt_rand(1, 10);
 $return = array_flip(array_flip($return));
 $count = count($return);
 } //www.jb51.net
foreach($return as $value)
 {
 echo $value." ";
 }
echo "<br/>";
$arr=array_values($return);// 获得数组的值 
foreach($arr as $key)
echo $key." ";
?>

<?php
function randpw($len=8,$format='ALL'){
$is_abc = $is_numer = 0;
$password = $tmp =''; 
switch($format){
case 'ALL':
$chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
break;
case 'CHAR':
$chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
break;
case 'NUMBER':
$chars='0123456789';
break;
default :
$chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
break;
} // www.jb51.net
mt_srand((double)microtime()*1000000*getmypid());
while(strlen($password)<$len){
$tmp =substr($chars,(mt_rand()%strlen($chars)),1);
if(($is_numer <> 1 && is_numeric($tmp) && $tmp > 0 )|| $format == 'CHAR'){
$is_numer = 1;
}
if(($is_abc <> 1 && preg_match('/[a-zA-Z]/',$tmp)) || $format == 'NUMBER'){
$is_abc = 1;
}
$password.= $tmp;
}
if($is_numer <> 1 || $is_abc <> 1 || empty($password) ){
$password = randpw($len,$format);
}
return $password;
}
for($i = 0 ; $i < 10; $i++){
echo randpw(8,'NUMBER');
echo "<br>";
}