Алексей

<?php
if($_GET['sort'] == $field and $_GET['dir'] == 'ASC') {$arr='&_uarr;';}
if($_GET['sort'] == $field and $_GET['dir'] == 'DESC') {$arr='&_darr;';}
if(!$_GET[$field]){
	if($_GET['dir'] == 'ASC'){
		$output = '<a href="'.$url.'?'.$q.'sort='.$field.'&dir=DESC#prod">'.$name.''.$arr.'</a>';
	} else {
		$output = '<a href="'.$url.'?'.$q.'sort='.$field.'&dir=ASC#prod">'.$name.''.$arr.'</a>';
	}
} else {
	$output = '<a href="'.$url.'?'.$q.'sort='.$field.'&dir=ASC#prod">'.$name.'</a>';
}
return $output;

<?php
$sort = $_GET['sort'];
if($sort == '') {
    $output='&sortby=`{"menuindex":"ASC"}`';
} else {
    $output = '&sortby=`{"'.$sort.'":"'.$_GET['dir'].'"}`';
}
return $output;

<div class="sort">
Сортировать: 
[[!sortLink? &url=`[[*uri]]` &field=`pagetitle` &name=`по названию`]]  
[[!sortLink? &url=`[[*uri]]` &field=`price` &name=`по цене`]]  
</div>
<div class="results">
[[!pdoResources?
&parents=`...`
&tpl=`...`
.........
[[!Sort]]
]]
</div>