vowelChek.php

<?php

$string = "Indonesia";

function vowelCheck($string)
{
   $lower = strtolower($string);
   $split = str_split($lower);
   $vowel = [];

   foreach ($split as $value) {
      if (preg_match('/^[aeiou]/i', $value)) {
         array_push($vowel, $value);
      }
   }

   $result = array_unique($vowel);

   echo "\"$string\" = " . count($result) . " huruf vokal, yaitu " . join($result, ", ");
   echo "\n";
}

vowelCheck($string);

// "Indonesia" = 4 huruf vokal, yaitu i, o, e, a