Help with search file and ignoring file extensions

Basically, below I have a search code where users can search through files and download them. However, if you search the extension, they all show, searching .gzr shows all of them. I want to ignore the file extension first of all, secondly, I want to be able to click a link like show all and all the files are listed.

My code is as follows:

<?php

include_once("setup.php");

$_POST['submit'] = addslashes($_POST['submit']); 

if(isset($_POST['submit']))  { 

    $search  =  addslashes(htmlspecialchars($_POST['searchword']));

    if ($search) { 

        $brackets = "";
        for($ix=0; $ix<strlen($search); $ix++) {
            $brackets .= sprintf("[%s%s]", strtoupper($search[$ix]), strtolower($search[$ix]));
        }

        foreach(glob($folder . "*$brackets*") as $filename) {
            $i++;
            $filelink = $filename;
            $filename = end(explode("/", $filename));
            echo "<a href=\"$filelink\">$filename</a>" . "<br />\n";
        }
        
        if ($i > 0) {
            echo "<br>$i File(s) Found";
        } else {
            echo "No files found.";
        }

    } else {
    
        echo "No keyword entered.";
    
    }
}

?>

PHP: