Example validation for chilean Rut. (credit https://gist.github.com/punchi/3a5c44e7aa7ac0609ce9e53365572541)

Rut.php

<?php

final class Rut {
  
/**
 * Check a valid Rut
 * @param  string $rut
 * @return boolean
 */
  public static function validate(string $rut): bool
  {
    if (!preg_match("/^[0-9.]+[-]?+[0-9kK]{1}/", $rut)) {
      return false;
    }
    $rut    = preg_replace('/[.-]/i', '', $rut);
    $dv     = substr($rut, -1);
    $number = substr($rut, 0, strlen($rut) - 1);
    $i      = 2;
    $sum    = 0;
    foreach (array_reverse(str_split($number)) as $v) {
      if ($i == 8) {
        $i = 2;
      }
      $sum += $v * $i;
      ++$i;
    }
    $dvr = 11 - ($sum % 11);
    if ($dvr == 11) {
      $dvr = 0;
    }
    if ($dvr == 10) {
      $dvr = 'K';
    }
    if ($dvr == strtoupper($dv)) {
      return true;
    }
    return false;
  }
}