Php String Split to Array

$str = 'one,two,three,four';
$arr=explode(",",$str);
dpr($arr);

--------Result 

Array
(
    [0] => one
    [1] => two
    [2] => three
    [3] => four
)

drupal mysql insert statement

$id = db_insert('pms_link_master')
      ->fields(array(
          'NODE_ID' => '1',
          'PMS_ID' => '2',
          'CLINIC_ID' => '415',
          'MASTER_TYPE' => 'location'
  ))
  ->execute();

http://alvinalexander.com/drupal/drupal-7-db_insert-query-sql-insert-db_query

drupal custom mysql statement

 $sql_query = db_query("select * from pms_link_master");
  echo "total rows ".$sql_query->rowCount();

    $sql_array = array();
    foreach ($sql_query as $row) {
        $reaged = (array) $row; // Standard object to array    
        $sql_array[] = $reaged;
    }
dpr($sql_array);