<?php
$fields = array();
$fields[1] = array("value" => "1", "text" => "Все");
$fields[2] = array("value" => "2", "text" => "Покупка");
$fields[3] = array("value" => "3", "text" => "Продажа");
foreach ($fields as $select) {
    $var = @$_POST["radio1"];
    $selected = ($select["value"] == $var) ? "checked" : "";
    echo '<input type="radio" name="radio1" value="' . $select["value"] . '"' . " " .
        $selected . '>' . $select['text'];
}
?>