生成任意长度的随机字符串，含有字母和数字

<?php

//随机生成n位字符串

function rand_str_n($num){

    $str = "qwertyuioplkjhgfdsazxcvbnmQAZWSXEDCRFVTGBYHNUJMIKOLP1234567890";

    $str_length = strlen($str)-1;

    $s='';

   for ($i = 0; $i < $num; $i++) {

      $s .= $str[rand(0, $str_length )];

   }

   return $s;

}

echo rand_str_n(6);

?>