Question

I want the DropDown text to be retained when the Form returns from POST. How to maintain the state?

Answer 1

You have to set the selected attribute on the option element.
See http://reference.sitepoint.com/html/option/selected

<form>
  <label for="favoritefood">Favorite food</label>
  <select name="favoritefood" id="favoritefood">
    <option value="che">Cheese</option>
    <option value="egg" selected="selected">Egg</option>
    <option value="cab">Cabbage</option>
  </select>
</form>

The $_POST array will either contain the numeric index of the option element or the value if this attribute is specified. In the example above, $_POST['favoritefood'] contains ‘egg’. You could build a helper that builds the option elements for you, e.g.

<?php
class HtmlHelper
{
    public static function option($value, $label, $selected)
    {
        $selected = ($value === $selected) ? ' selected="selected"' : '';
        return sprintf('<option value="%s"%s>%s</option>%s',
                       $value, $selected, $label, PHP_EOL);
    }
}
// Usage to get the above Selectbox options
echo HtmlHelper::option('che', 'Cheese', $_POST['favoritefood']),
     HtmlHelper::option('egg', 'Egg', $_POST['favoritefood']),
     HtmlHelper::option('cab', 'Cabbage', $_POST['favoritefood']);

Of course, it would be smarter to have a Selectbox helper instead which you can pass the options and the POST array in one go, instead of calling it for each option separately. I leave it up to you to build this.

If you are not building your Select options dynamically with PHP, you can select the option by adding a small javascript to your page that you pass the value set for favoritefood from the $_POST array and have the script select the option. See the answers to this question for possible code.