php 随机生成10位字符代码

function randStr($len) 
{ 
$chars='ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz'; // characters to build the password from 
$string=''; 
for(;$len>=1;$len--) 
{ 
$position=rand()%strlen($chars); 
$string.=substr($chars,$position,1); 
} 
return $string; 
} 
echo randStr(10)."<br>";