生成随机字符串

function str_rand($length = 10, $characters = '0123456789abcdefghijklmnopqrstuvwxyz'){
if(!is_int($length) || $length < 0){
return false;
}
$characters_length = strlen($characters) - 1;
$string = '';
for($i = 0; $i<$length; $i++){
$string .= $characters[random_int(0,$characters_length)];
}
return $string;
}

print str_rand(5,'02312abcd1');