PHP无法上载excel工作表或大写格式文件

我一直试图让我的上传功能上传excel表格，但我得到的是无效的格式

我尝试删除if语句以检查文件格式，但仍然无法上载除“jpg”“jpeg”“png”“pdf”以外的任何内容

wierdly如果尝试上载标题化格式（如JPG或PDF）的文档/图像，则会显示相同的错误：“错误：请选择有效的文件格式。”

<?php 
// Check if the form was submitted
date_default_timezone_set("Asia/Bahrain");
if($_SERVER["REQUEST_METHOD"] == "POST"){
    // Check if file was uploaded without errors
   // if(isset($_FILES["file"]) || !isset($_POST['RRidupload']) && $_FILES["photo"]["error"] == 0 )
     if(isset($_FILES["file"])){
        echo "<pre>";
        //$allowed = array("jpg" => "image/jpg", "jpeg" => "image/jpeg", "gif" => "image/gif", "png" => "image/png", "pdf" => "application/pdf", "pdf" => "application/pdf");
        $allowed = array('jpg', 'jpeg','png','pdf','PDF','JPG','xlsx','xls');
        foreach($_FILES["file"]["name"] as $key=>$val){
        $filename = $_FILES["file"]["name"][$key];
        $filetype = $_FILES["file"]["type"][$key];
        $filesize = $_FILES["file"]["size"][$key];

        // Verify file extension
        $ext = pathinfo($filename, PATHINFO_EXTENSION);
        if(!array_key_exists($ext, $allowed)) die("Error: Please select a valid file format.");

        // Verify file size - 5MB maximum
        $maxsize = 5 * 1024 * 1024;
        if($filesize > $maxsize) die("Error: File size is larger than the allowed limit.");
        $RR_id = $_POST['RRidupload']; // required
        if (!file_exists('upload/'. $RR_id)) {
            mkdir('upload/'. $RR_id, 0777, true);
        }
        // Verify MYME type of the file
        if(in_array($filetype, $allowed)){
            // Check whether file exists before uploading it
            if(file_exists("upload/". $RR_id . "/" . $filename)){
                echo $filename . " is already exists.";
            } else{
                move_uploaded_file($_FILES["file"]["tmp_name"][$key], "upload/". $RR_id . "/" . $filename);
                echo "Your file was uploaded successfully.";
            } 
        } else{
            echo "Error: There was a problem uploading your file. Please try again."; 
        }
            }
    } else{
        echo "Error: " . $_FILES["file"]["error"];
    }
}
?>