<?php
$state_sql=null;
$city_sql="SELECT pkg_id FROM package_city where city_id in (1)";
$category_sql="SELECT pkg_id FROM package_category where category_id in (2)";
$sub_category_sql=null;
$package_sql="SELECT pkg_id FROM package where id in (3, 4)";

$sql_get_any_packages = array(
    $state_sql,
    $city_sql,
    $category_sql,
    $sub_category_sql,
    $package_sql);
$sql_get_any_packages = array_filter($sql_get_any_packages);
$sql_get_any_packages = implode(" union ", $sql_get_any_packages);
echo($sql_get_any_packages);
?>