PHP 取得随机字符串

getCode($length, $mode);
*/
function getCode ($length = 32, $mode = 0)
{
switch ($mode) {
case '1':
$str = '1234567890';
break;
case '2':
$str = 'abcdefghijklmnopqrstuvwxyz';
break;
case '3':
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
break;
case '4':
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
break;
case '5':
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
break;
case '6':
$str = 'abcdefghijklmnopqrstuvwxyz1234567890';
break;
default:
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890';
break;
}
$result = '';
$l = strlen($str);
for($i = 0;$i