Partial caching of snippet code?

<?php
$i = 0;
$title_a = $value_a = [];

$XML = new DOMDocument();
$XML->load($url);
$xpath = new DOMXPath($XML);

foreach ($xpath->query("//channel/item/season/*/title") as $title_node) {
	$title_a[] .= $title_node->nodeValue;
}
foreach ($xpath->query("//channel/item/season/*/value") as $value_node) {
	$value_a[] .= $value_node->nodeValue;
}

$season_a = explode(',',$_GET['season']);

while ($i <= 12) {
	$output .= '<div class="col-xs-6">';
	if(in_array($i, $season_a)){
		$output .= '<a href="" class="btn-xs btn-block filter-pill btn-success">';
		$output .= $title_a[$i];
		$output .= '<i class="icon-cross"></i></a>';
	} else {
		$output .= '<a href="" class="btn-xs btn-block filter-pill btn-default">';
		$output .= $title_a[$i];
		$output .= '<span class="badge pull-right">' . $value_a[$i] . '</span></a>';
	}
	$output .= '</div>';
    $i++; 
}
return($output);