Mask (cell) phone number with asterisk

mask_cell.php

function mask_cell($cell) {
    $cell_array = explode(' ', $cell);
    $length = count($cell_array);
    $masked = '';
    
    for ($i = 0; $i < count($cell_array); $i++) {
      if ($i != ($length - 2)) {
        $masked .= $cell_array[$i];
      } else {
        $masked .= str_repeat('·', strlen($cell_array[$i]));
      }
      
      if ($i != ($length - 1)) {
       $masked .= '-';
      }
    }
    
    return $masked;
}