Question

How can I add/improvised my code so Spanish accent will be considered as valid in addition to normal alphabet (a-z)

I have the following in my code

public static function IsAlpha($s){
  $reg = "#[^a-z\s-]#i";
  $count = preg_match($reg, $s, $matches);
  return $count == 0;
}

Answer 1

As found in the answer to this question, you could match accented characters using the full Letter Unicode property \p{L}. That includes regular a-z characters along with accented ones, so replace a-z in your expression with this like so:

$reg = "#[^\p{L}\s-]#u";

Note that to use this you need the UTF-8 modifier u after your closing delimiter, as the docs say such Unicode “character types are available when UTF-8 mode is selected“.