dynamic selection (PHP +javascript)

[jansky]

I know this is not purely related to php script but if there is someone guru who already solved this kind of problem

How do I have the list of OPTIONs in a SELECT listbox change depending on the selection in another listbox?
example for this is

you have one listbox which selects the country then you have a second which should only display the valid states/province for that country, or one listbox which shows categories and another which lists the subcategories for that category, etc...

Thanks in advance

[devinemke]

a simple example (using only PHP, no JS):

<?php
$categories = array(
'catA' => array('subcatA1', 'subcatA2', 'subcatA3'),
'catB' => array('subcatB1', 'subcatB2', 'subcatB3'),
'catC' => array('subcatC1', 'subcatC2', 'subcatC3')
);

echo '
<form action="" method="POST">
category:<br>
<select name="cat">
';

foreach ($categories as $key => $value)
{
	echo '<option';
	if (isset($_POST['cat']) && $_POST['cat'] == $key) {echo ' selected';}
	echo '>' . $key;
}

echo '
</select>
<br>
<br>
';

if (isset($_POST['cat']))
{
	echo '<select name="subcat">';	
	foreach ($categories[$_POST['cat']] as $value)
	{

	echo '<option';
	if (isset($_POST['subcat']) && $_POST['subcat'] == $value) {echo ' selected';}
	echo '>' . $value;
}
echo '
</select>
<br>
<br>
';
}

echo '
<input type="submit" name="submit" value="submit">
</form>
';
?>