php - How can I run a function with an array of checkbox values passed as an argument?

So I'm wanting to run a function EVERY TIME a user clicks thebtnChangeCat button...Im having trouble and I'm really not sure how to get it to work!

Im trying to runshowCategory($_POST['chkCat'], 1)[0];and pass it the array of checked checkboxes when the user clicks thebtnChangeCat button. Im not sure why this isn't working??

I've literally searched everywhere for a WORKING solution but can't find one that will work when passing the values to a function!

    $showVideos = showCategory($categories, 1)[0];
    $rowLength = showCategory($categories, 1)[3];
    $likes = showCategory($categories, 1)[1];
    $dislikes = showCategory($categories, 1)[2];
?>
<main>

    <div class='controller-wrap'>
        <div class='content-wrap'>
        <h3>Category: </h3>hp

            <form action='most-liked.php' method='post'>
                <?php
                    $allCategories = ["All", "Sport", "Automotive", "Comedy", "Misc", "Surfing"];
                    $htmlOutput = "";
                    $i=0;
                        for($i;$i<sizeof($allCategories);$i++)
                        {
                            if($allCategories[$i] == "Surfing"){
                                $htmlOutput .= "<input selected type='checkbox' name='chkCat[]' value='".$allCategories[$i]."'/>";
                            }
                            else{
                                $htmlOutput .= "<input type='checkbox' name='chkCat[]' value='".$allCategories[$i]."'/>";
                            }
                        }   
                    echo $htmlOutput;
                ?>

            </form>
            <br />
        if(isset($_POST['chkCat'])){
            if(is_array($_POST['chkCat'])) {
                foreach($_POST['chkCat'] as $value){
                  echo $value;
                }
            }else{
                    $value = $_POST['chkCat'];
                    echo $value;
                }
                // showCategory($_POST['chkCat'], 1)[0];
        }
        isset($_POST['btnChangeCat'])){
            // //How can I run this function with the array of CHECKBOXES??
            showCategory($_POST['chkCat'], 1)[0];
        }
        ?>
        <input type='submit' value='CHANGE CATEGORIES' class='btnlike btnLike' name='btnChangeCat'/>
    </div>
</main>
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