Best way to only search for Excel files - php

Question

So I've made this Upload file function on my php page. What this function does is uploading the file into a folder with the same name as the file. The user can choose a lot of different projects, from a dropdown. When the user picks a project with a existing file, another function will scan all the information from the Excel file.
My question here is:
How can I search for only existing Excel files, and not every single file in the directory?
Code:
/**
* Checks if there is an existing uploaded RVTM file. File was uploaded through 'upload.php'.
*
* #access public
* #param string $fileName Name of the spreadsheet file
* #param array $OverviewResult Array of information about verdicts, TestSuiteCollectionIds, and TestJobIds
* #author Mads Sander Hoegstrup
*/
function Create_Table_RVTM($fileName, $OverviewResult){
#Scan directory for any files, and return them (should only be a single file), when the file is deleted the directory is whiped clean: Delete_RVTM_file(...)
$dir = "./DashboardFiles/files/".$fileName;
$FindFiles = scandir($dir);
$files = array_values(array_diff($FindFiles, array('.', '..')));
if ($files) {
$path = "./DashboardFiles/files/".$fileName."/".$files[0];
echo "<br>The file $fileName exists";
RVTM_Excel($fileName, $OverviewResult, $path);
}else {
echo "<br>The file $fileName does not exists";
}
}

Answer 1

You can use PHP builds in glob with a wildcard something like
<?php
foreach (glob("/path/to/folder/*.xl*") as $filename) {
echo "$filename size " . filesize($filename) . "\n";
}
?>

Answer 2

You can do it by looking at the file extension, for example .xls.
Here is the full list
https://support.microsoft.com/en-us/office/file-formats-that-are-supported-in-excel-0943ff2c-6014-4e8d-aaea-b83d51d46247
.xlsx
.xlsm
.xlsb
.xltx
.xltm
.xls
.xlt
.xls
.xlam
.xla
.xlw
.xlr
and here you can see how to get a file extension
$ext = pathinfo($path, PATHINFO_EXTENSION);
and read the directory using spl
https://www.the-art-of-web.com/php/directory-list-spl/
use \DirectoryIterator;
function getFileList($dir)
{
// array to hold return value
$retval = [];
// add trailing slash if missing
if(substr($dir, -1) != "/") $dir .= "/";
// open directory for reading
$d = new DirectoryIterator($dir) or die("getFileList: Failed opening directory $dir for reading");
foreach($d as $fileinfo) {
// skip hidden files
if($fileinfo->isDot()) continue;
$retval[] = [
'name' => "{$dir}{$fileinfo}",
'type' => ($fileinfo->getType() == "dir") ? "dir" : mime_content_type($fileinfo->getRealPath()),
'size' => $fileinfo->getSize(),
'lastmod' => $fileinfo->getMTime()
];
}
return $retval;
}