how to retain drop-down menu selected state and display error if not selected

[errcricket]

hello. i have a form that checks for validation and does not connect w/database until is ok. for drop down menus i have 2 concerns:

1. it should retain field input for any reposts

2. if a previous option is checked, then they must select an item from the drop down menu. if not, an error message appears.

 

<label for="X" maxlength="2">X: </label>
<select id="x" name="x" maxlength="2" VALUE="<?php if(isset($_POST['x'])) echo $x; ?>"/>
<option <?php   if ($_POST['x'] == "-"){ echo "selected";} ?> >-</option>
<option <?php   if ($_POST['x'] == "y"){ echo "selected";}?> >y</option>
<option <?php   if ($_POST['x'] == "z"){ echo "selected";}?> >z</option>
.
.
</select>    

 

not sure about efficiency, but this makes the values sticky. unfortunately is also has a "Notice: undefined index..." initially in the box (i will turn off the error msg later).  if user choices require a selection from the menu but nothing is selected, the error message will not appear until they have tried to submit 2 times.

 

how can i define something that has not been selected yet?

 

i also tried below, but was unable to get it to stick at all.

 

<label for="x" maxlength="2">X: </label>
<select name="xy" size="1" maxlength="2" >
<?php 
$xy= array ('-', 'y', 'z',... .');
print_r($xy);
foreach ($xy as $optValue)
{
    $selected = ($optValue == $_POST['x']) ? ' selected="selected"' : '';
    echo "<option value=\"{$optValue}\"{$selected}>{$optValue}</option>\n";
}
echo "</select>\n";
  
?>
</select>   

 

does anyone have any suggestions? thanks in advance.

 

p.s. if user chooses the non-required option, the default is/should be "-"