使用RegEx限制字符串长度

Question

I wrote this regex for checking the input number from my form:

if (!preg_match("/^0\d{10}+|^9\d{9}+/",$_POST['number'])){
   echo "Error";
}else{
   echo "Ok";
}

this code will check the minimum length but if length is more than 10 or 9 characters, this regex cannot work !

What should I do ? should I check with strlen after Regex or I can limit the maximum length ?

UPDATE:

the string length should be exactly 10 characters if start with 0 and should be exactly 9 characters if start with 9, and should return false on another ways (more or less length, start with different numbers and ...)

Answer 1

Possibly you just want to anchor the string at the end using $. Also can drop the + after the numeric quantifier:

^(?:0\d{9}|9\d{8})$

See test at regex101.com