How to add internal lines to a HTML table?

This is how my current table looks like:

I would prefer the table has no border but contains internal lines. That means there should only be 8 horizontal lines. How do I achieve this?

Here are my codes:

<table class="table">
  <?php
      $file = fopen("Book1.csv","r");
      $data = array();
      while($row = fgetcsv($file)) {
      $data[] = $row; //Get all the data 
      }
      if($data){
          $n_columns = count($data[0]); //Get number of columns 
      }
      echo '<table border="0">'; 
      for ($col = 0; $col < $n_columns; $col++) {
          echo '<tr>';
          foreach ($data as $row_k => $row) {
              if ($row_k == 0) {
                  echo '<th>';
              } else {
                  echo '<td>';
              }

              echo $row[$col] ?? '';
              if ($row_k == 0) {
                  echo '</th>';
              } else {
                  echo '</td>';
              }
          }
          echo '</tr>';
      }
      echo '</table>';
  ?>
</table>  

<style type="text/css">
  table{
    border-color: #17a2b8;
  }
</style>

>Solution :

Try this:

table {
    border-collapse: collapse;
    width: 100%;
}

tr {
    border-bottom: 1px solid #17a2b8;
}