title: How to insert an actual NULL value into a nullable column?
body: <pre><code>function save($gmt, $name, $address, $phone, $remark)
  {
      $query= "INSERT INTO `user` (`gmt`, `name`, `address`, `phone`, `remark`) VALUES ('$gmt', '$name', '$address', '$phone', '$remark')";
      mysql_query($query);
  }
  </code></pre>
  
  <p>Here, address, phone, and remark can be <code>NULL</code>. I need it to save <code>NULL</code> whenever the variable is set to <code>NULL</code> and the column is nullable, instead of inserting an empty string. </p>
  
  <p>How can I insert <code>NULL</code> value into the database using PHP? </p>