function generateRandomString($length = 10) {

<?php
//RandomString.php
header("Content-type: text/html; charset=utf-8");
//2、PHP生成随机字符串
//
//当我们需要生成一个随机名字，临时密码等字符串时可以用到下面的函数：

function generateRandomString($length = 10) { 
    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; 
    $randomString = ''; 
    for ($i = 0; $i < $length; $i++) { 
        $randomString .= $characters[rand(0, strlen($characters) - 1)]; 
    } 
    return $randomString; 
}
//使用方法如下：
$str=generateRandomString(5);
echo $str , '<br>';
?>