/**
* 随机字符
* @param number $length 长度
* @param string $type 类型
* @param number $convert 转换大小写
* @return string
*/
function random($length=6, $type='string', $convert=0){
$config = array(
'number'=>'1234567890',
'letter'=>'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',
'string'=>'abcdefghjkmnpqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ23456789',
'all'=>'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890'
);
if(!isset($config[$type])) $type = 'string';
$string = $config[$type];
$code = '';
$strlen = strlen($string) -1;
for($i = 0; $i < $length; $i++){
$code .= $string{mt_rand(0, $strlen)};
}
if(!empty($convert)){
$code = ($convert > 0)? strtoupper($code) : strtolower($code);
}
return $code;
}
