Example filter form with pagination

example-filter-form.php

<?php namespace ProcessWire;

$filter = "";

$form = $modules->InputfieldForm;
$form->attr("action", $page->url);
$form->attr("method", "get");

// select with sort options
$f = $modules->InputfieldSelect;
$f->attr("name", "sort");
$f->label = "Sort";
$f->addOptions(array(
	"-title" => "descending",
	"title" => "ascending"
));
$form->add($f);

// submit button
$f = $modules->InputfieldSubmit;
$f->attr("name", "filter");
$form->add($f);

// process form
if(count($input->get)){
	// process form input and populate fields
	$form->processInput($input->get);

	// if sort is not empty
	if($form->get("sort")->value) {
		// build filter and add to whitelist so it gets picked up by pagination
		$input->whitelist("sort", $sanitizer->text($form->get("sort")->value));
		$filter .= ",sort=" . $input->whitelist("sort");
	}
}

$result = $pages->find("template=basic-page, limit=2{$filter}");

$content .= "<h2>Show Results</h2>";

if(!$result->count) {
	$content .= "<p>no results</p>";
} else {
	foreach($result as $res){
		$content .= "<p>$res->title<br>$res->url</p>";
	}
	$content .= $result->renderPager();
}

$content .= $form->render();