在PHP简单验证中使用正则表达式的问题

I am trying to learn Regular Expression in PHP by creating simple samples.Here I have very simple example as:

if($_POST){
   $errors = array();

  if(isset($_POST['name'])){
     if(!preg_match('/^([a-zA-Z]{3,8})$/',$_POST['name'])){
       $errors['name1'] = "Must enter Alphabet";
       $errors['name2'] = ""Cant be less than 3";
     }

  }
  if(count($errors)==0){
  header("Location: pro.php");
  exit();
  }
}
?>

<form method="POST" target="">
First name: <input type="text" name="name"><br>
<input type="submit" name="submit">
</form>

To me, the validation is working fine but I have problem on presenting error message based on error.For example I would like to display error $errors['name1'] ONLY when not string has entered and $errors['name2'] while numbers entered. I tried to separate expression into two criteria as:

if(isset($_POST['name']))
   {
     if(!preg_match('/^([a-zA-Z])$/',$_POST['name']))
     {
       $errors['name1'] = "Must enter Alphabet";
     }
      if(preg_match('/^{3,8}$/',$_POST['name']))
     {
       $errors['name2'] = "Cant be less than 3";
     }
   }

but I am getting following error

Update

if(isset($_POST['name']))
   {
     if(!preg_match('/^([a-zA-Z])$/',$_POST['name']))
     {
       $errors['name1'] = "Must enter Alphabet";
     }
      if ( ! preg_match( '/.{3,8}/', $_POST['name'] ))
     {
       $errors['name2'] = "Cant be less than 3";
     }
   }

Ok I am going to answer my question.Thanks to Masud Alam I figure it out how to do this in Regular Expression. The hint is using

 if (!preg_match('/^[a-z]+$/i', $_POST['name'])) {
     //
 }

 if (!preg_match('/^.{3,25}$/', $_POST['name'])) {
     //
 }

it works for me so far!

The error you are seeing is the result of not specifying match criteria in the regex before the {} operator. If you only care whether at least three of ANY character had been entered, try

if ( ! preg_match( '/.{3,8}/', $haystack ) )

You have to provide an 'atom' for the range to count. In this case, '.' signifies any single character.

How about:

if (isset($_POST['name'])) {
    if (preg_match('/[^a-z])/i', $_POST['name'])) {
        $errors['name1'] = "Must enter Alphabet";
    }
    if ( strlen($_POST['name']) < 3) {
        $errors['name2'] = "Cant be less than 3";
    }
    if ( strlen($_POST['name']) > 8) {
        $errors['name3'] = "Cant be more than 8";
    }
}

If you really want to use regex:

if (preg_match('/[^a-z])/i', $_POST['name'])) {
    $errors['name1'] = "Must enter Alphabet";
}
if ( ! preg_match('/^.{3,8}$/', $_POST['name']) ) {
    $errors['name2'] = "Cant be less than 3";
}