PHP Select optgroup from array

I have a array that contains continent and with countries.

[php]
Array
(
[0] => Array
(
[continent_name] => asia
[country_name] => pakistan
[country_value] => 1
)

[1] => Array
(
[continent_name] => asia
[country_name] => india
[country_value] => 2
)

[2] => Array
(
[continent_name] => asia
[country_name] => china
[country_value] => 3
)

[3] => Array
(
[continent_name] => asia
[country_name] => bangladesh
[country_value] => 4
)

[4] => Array
(
[continent_name] => antarctica
[country_name] => 123
[country_value] => 10
)

[5] => Array
(
[continent_name] => europe
[country_name] => canada
[country_value] => 5
)

[6] => Array
(
[continent_name] => europe
[country_name] => germany
[country_value] => 6
)

[7] => Array
(
[continent_name] => europe
[country_name] => sweden
[country_value] => 7
)

[8] => Array
(
[continent_name] => asia
[country_name] => iraq
[country_value] => 8
)

[9] => Array
(
[continent_name] => antarctica
[country_name] => abc
[country_value] => 8
)

[10] => Array
(
[continent_name] => antarctica
[country_name] => xyz
[country_value] => 9
)

)
[/php]

Now we need to reorder this array.

[php]
foreach($continent_countries as $array_key=>$array_values) {
$new_array = $array_values[‘continent_name’];
$new_sel_array[$new_array][] = array(‘c_name’ => $array_values[‘country_name’], ‘c_value’ => $array_values[‘country_value’]);
}
[/php]

array has been reorder with continent

[php]
Array
(
[asia] => Array
(
[0] => Array
(
[c_name] => pakistan
[c_value] => 1
)

[1] => Array
(
[c_name] => india
[c_value] => 2
)
[2] => Array
(
[c_name] => china
[c_value] => 3
)
[3] => Array
(
[c_name] => bangladesh
[c_value] => 4
)
[4] => Array
(
[c_name] => iraq
[c_value] => 8
)

)
[antarctica] => Array
(
[0] => Array
(
[c_name] => 123
[c_value] => 10
)
[1] => Array
(
[c_name] => abc
[c_value] => 8
)
[2] => Array
(
[c_name] => xyz
[c_value] => 9
)
)
[europe] => Array
(
[0] => Array
(
[c_name] => canada
[c_value] => 5
)
[1] => Array
(
[c_name] => germany
[c_value] => 6
)
[2] => Array
(
[c_name] => sweden
[c_value] => 7
)
)
)
[/php]

now set select with option group

[php]
echo ‘<select>’;
foreach($new_sel_array as $sel_opt=>$sel_opt_array){
echo ‘<optgroup label="’.$sel_opt.’"></optgroup>’;
$for_limit = count($sel_opt_array);
for($sel_inc=0; $sel_inc<$for_limit; $sel_inc++) {
$c_name = $sel_opt_array[$sel_inc][‘c_name’];
$c_value = $sel_opt_array[$sel_inc][‘c_value’];
echo ‘<option value="’.$c_value.’">’.$c_name.'</option>’;
}
}
echo ‘</select>’;
[/php]