FUNCTIONS.php

function footyboots_construct_filter_query() {
            if(isset($_GET['producent'])) {
                $producentGET1 = $_GET['producent'];
                $producentGET = true;
            } else {
                $producentGET = false;
            }
            if(isset($_GET['produkttype'])) {
                $produkttypeGET1 = $_GET['produkttype'];
                $produkttypeGET = true;
            } else {
                $produkttypeGET = false;
            }
            if(isset($_GET['farve'])) {
                $farveGET1 = $_GET['farve'];
                $farveGET = true;
            } else {
                $farveGET = false;
            }
            if(isset($_GET['knopkonfiguration'])) {
                $knopkonfigurationGET1 = $_GET['knopkonfiguration'];
                $knopkonfigurationGET = true;
            } else {
                $knopkonfigurationGET = false;
            }
            if(isset($_GET['tilbud'])) {
                $tilbudGET1 = $_GET['tilbud'];
                $tilbudGET = true;
            } else {
                $tilbudGET = false;
            }

            $argsFilter = array(
                'post_type' => 'fodboldstoevle',
                'showposts' => -1,
                'meta_query' => array(
                    ($producentGET) ? array('key' => 'footyboots_producent','value' => $producentGET1) : null,
                    ($produkttypeGET) ? array('key' => 'footyboots_produkttype','value' => $produkttypeGET1) : null,
                    ($farveGET) ? array('key' => 'footyboots_farve','value' => $farveGET1) : null,
                    ($knopkonfigurationGET) ? array('key' => 'footyboots_knopkonfiguration','value' => $knopkonfigurationGET1) : null,
                    ($tilbudGET) ? array('key' => 'footyboots_tilbud','value' => $tilbudGET1) : null,
                ),

            );

            print_r($argsFilter);
            return $argsFilter;
}






STOEVLEFILTER.php

<?php
/* Template Name: Fodboldstøvle filter */
get_header();
?>
<div class="container">
<h1>Støvler</h1>
<div class="row">
    <div class="col-md-3">
        <button class="filter-btn visible-xs visible-sm" data-toggle="collapse" data-target="#filter-md">Vis filter</button>
        <div id="filter-md" class="sidebar collapse.in">
            <form action="<?php the_permalink(); ?>" method="GET">
                <section>
                    <b>Pris</b>
                    <ul class="filter-checkboxes">
                        <li><input type="checkbox" id="checkboxTilbud" name="tilbud[]" value="tilbud"><label for="checkboxTilbud"><span></span>Vis kun tilbudsvarer</label></li>
                    </ul>
                </section>
                <section>
                    <b>Mærke</b>
                    <ul class="filter-checkboxes">
                        <li><input type="checkbox" id="checkboxAdidas" name="producent[]" class="producent123" value= adidas"><label for="checkboxAdidas"><span></span>adidas</label></li>
                        <li><input type="checkbox" id="checkboxNike" name="producent[]" class="producent123" value="Nike"><label for="checkboxNike"><span></span>Nike</label></li>
                        <li><input type="checkbox" id="checkboxPuma" name="producent[]" class="producent123" value="Puma"><label for="checkboxPuma"><span></span>Puma</label></li>
                    </ul>
                </section>
                <section>
                    <b>Produkt type</b>
                    <ul class="filter-checkboxes">
                        <li><input type="checkbox" id="checkboxStoevler" name="produkttype[]" value="Fodboldstøvler"><label for="checkboxStoevler"><span></span>Fodboldstøvler</label></li>
                        <li><input type="checkbox" id="checkboxIndendoers" name="produkttype[]" value="Indendørssko"><label for="checkboxIndendoers"><span></span>Indendørssko</label></li>
                        <li><input type="checkbox" id="checkboxKunstgraes" name="produkttype[]" value="Kunstgræsstøvler"><label for="checkboxKunstgraes"><span></span>Kunstsgræsstøvler</label></li>
                        <li><input type="checkbox" id="checkboxGrus" name="produkttype[]" value="Grusbanestøvler"><label for="checkboxGrus"><span></span>Grusbanestøvler</label></li>
                    </ul>
                </section>
                <section>
                    <b>Farve</b>
                    <ul class="filter-checkboxes">
                        <li><input type="checkbox" id="checkboxBlaa" name="farve[]" value="Blå"><label for="checkboxBlaa"><span></span>Blå</label></li>
                        <li><input type="checkbox" id="checkboxBrun" name="farve[]" value="Brun"><label for="checkboxBrun"><span></span>Brun</label></li>
                        <li><input type="checkbox" id="checkboxGraa" name="farve[]" value="Grå"><label for="checkboxGraa"><span></span>Grå</label></li>
                        <li><input type="checkbox" id="checkboxGroen" name="farve[]" value="Grøn"><label for="checkboxGroen"><span></span>Grøn</label></li>
                        <li><input type="checkbox" id="checkboxGul" name="farve[]" value="Gul"><label for="checkboxGul"><span></span>Gul</label></li>
                        <li><input type="checkbox" id="checkboxGuld" name="farve[]" value="Guld"><label for="checkboxGuld"><span></span>Guld</label></li>
                        <li><input type="checkbox" id="checkboxHvid" name="farve[]" value="Hvid"><label for="checkboxHvid"><span></span>Hvid</label></li>
                        <li><input type="checkbox" id="checkboxLilla" name="farve[]" value="Lilla"><label for="checkboxLilla"><span></span>Lilla</label></li>
                        <li><input type="checkbox" id="checkboxOrange" name="farve[]" value="Orange"><label for="checkboxOrange"><span></span>Orange</label></li>
                        <li><input type="checkbox" id="checkboxRoed" name="farve[]" value="Rød"><label for="checkboxRoed"><span></span>Rød</label></li>
                        <li><input type="checkbox" id="checkboxSort" name="farve[]" value="Sort"><label for="checkboxSort"><span></span>Sort</label></li>
                        <li><input type="checkbox" id="checkboxSoelv" name="farve[]" value="Sølv"><label for="checkboxSoelv"><span></span>Sølv</label></li>
                    </ul>
                </section>
                <section>
                    <b>Knopkonfiguration</b>
                    <ul class="filter-checkboxes">
                        <li><input type="checkbox" id="checkboxAG" name="knopkonfiguration[]" value="AG"><label for="checkboxAG" data-toggle="tooltip" data-placement="right" title="Artificial Grass - Kunstgræs"><span></span>AG</label></li>
                        <li><input type="checkbox" id="checkboxFG" name="knopkonfiguration[]" value="FG"><label for="checkboxFG" data-toggle="tooltip" data-placement="right" title="Firm Ground - Naturlige græsbaner"><span></span>FG</label></li>
                        <li><input type="checkbox" id="checkboxHG" name="knopkonfiguration[]" value="HG"><label for="checkboxHG" data-toggle="tooltip" data-placement="right" title="Hard Ground - Grus & kunstgræs"><span></span>HG</label></li>
                        <li><input type="checkbox" id="checkboxIC" name="knopkonfiguration[]" value="IC"><label for="checkboxIC" data-toggle="tooltip" data-placement="right" title="Indendørssko"><span></span>IC</label></li>
                        <li><input type="checkbox" id="checkboxSG" name="knopkonfiguration[]" value="SG"><label for="checkboxSG" data-toggle="tooltip" data-placement="right" title="Soft Ground - Blød vandet jord, typisk jernknopper"><span></span>SG</label></li>
                        <li><input type="checkbox" id="checkboxTF" name="knopkonfiguration[]" value="TF"><label for="checkboxTF" data-toggle="tooltip" data-placement="right" title="Artificial Grass - Kunstgræs"><span></span>TF</label></li>
                    </ul>
                </section>
                <input class="filter-btn" type="submit" id="filter_submit_btn" value="Find støvle">
            </form>
        </div>
    </div>
    <div class="col-md-9">
        <div class="row products">
            <?php
            $filterQuery = new WP_Query(footyboots_construct_filter_query());
            if($filterQuery->have_posts()):
                while($filterQuery->have_posts() ): $filterQuery->the_post();?>
                <div class="col-md-3 col-sm-6">
                    <div class="product-preview">
                        <?php
                        if(footyboots_check_tilbud(rwmb_meta('footyboots_tilbudprocent'))) { ?>
                        <div class="tilbud">
                            <?php
                            echo '-' . rwmb_meta('footyboots_tilbudprocent') .'%';
                            ?>
                        </div>
                        <?php
                        }
                        footyboots_return_first_image(rwmb_meta('footyboots_produktbilleder'));
                        ?>
                        <b><?php echo rwmb_meta('footyboots_producent'); ?></b>
                        <small><?php echo rwmb_meta('footyboots_navn') .' '.footyboots_implode('/', rwmb_meta('footyboots_knopkonfiguration')) .' '. footyboots_implode('/', rwmb_meta('footyboots_farve')); ?></small>
                        <div class="text-center">
                            <a href="<?php echo the_permalink(); ?>" class="btn btn-danger "><span class="glyphicon glyphicon-shopping-cart" aria-hidden="true"></span> DKK <?php echo rwmb_meta('footyboots_pris'); ?>,-</a>
                        </div>
                    </div>
                </div>
                <?php
                endwhile;
            else:
                ?>
                Ingen støvler matcher din søgning:(
                <?php
            endif;

            wp_reset_postdata();
            ?>
        </div>
    </div>
</div>
</div>
<?php get_footer(); ?>