PHP随机字符串生成代码(包括大小写字母)

function createRandomStr($length){
$str = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';//62个字符
$strlen = 62;
while($length > $strlen){
$str .= $str;
$strlen += 62;
}
$str = str_shuffle($str);
return substr($str,$length);
}
echo createRandomStr(10);

function createRandomStr($length){
$str = array_merge(range(0,9),range('a','z'),range('A','Z'));
shuffle($str);
$str = implode('',array_slice($str,$length));
return $str;
}
echo createRandomStr(10);