create a counter
$count = 0;
foreach( $images as $image ) {
// when outputing the element something like this
// I haven't a clue where you're trying to add this class in the code you provided
// I'm just guessing that it in the li
// some code here ......
?>
<li class="orbit-slide <?php
if ($count == 0) {
echo 'is-active';
}
?>">
<?php
// some more code here
// increment count before end loop
$count++;
} // end foreach
