preg_matchvalidation

Okay, everything I've checked on this site referring to validation isn't what I'm looking for.

What I'm looking to do is a minimum length and maximum length of a value in firstname and secondname, this is the code which I currently have.

        if (isset($_POST['submit'])) {
         $errors = array();
 
                  if (isset($_POST['firstname'])) {
             $fn = $_POST['firstname'];
         } else {
             $errors[] = "You have not entered a first name";
         }
 
         if (isset($_POST['secondname'])) {
             $sn = $_POST['secondname'];
         } else {
             $errors[] = "You have not entered a second name";
         }
 

I was just wondering how would I apply preg_match to those which the minimum is 4 letters and the maximum is 15?

I do know it's something to do with

if(preg_match('/^[A-Z \'.-]{4,15}$/i', $_POST['firstname']))
 

In doing this I tried to do

    if (isset($_POST['firstname']) && preg_match('/^[A-Z \'.-]{4,15}$/i', $_POST['firstname')) {
 

But that also gave me an error :/

Could anyone give me a solution for this?

Thanks!

UPDATE:-

Nvm, I found a way around it. I just did this

if (isset($_POST['firstname'])) {
         if (preg_match('/^[A-Z \'.-]{4,15}$/i', $_POST['firstname'])) {
             $fn = $_POST['firstname'];
         } else {
             $errors[] = "<center> <h3> You must enter between 4 and 15 characters! </h3></center>";                  
         }
     } else {
         $errors[] = "You have not entered a name";
 

}
For both the firstname and secondname. :)

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