PHP - Simple file upload

PHP - simple file upload.php

<?php
/*
|--------------------------------------------------------------------------
| Upload file
|--------------------------------------------------------------------------
| On submit upload file to folder and return excel array
|
*/
if($_POST){
    //helper and config variables
    $isUploaded  = false;
    $upload_path = "uploads/";

    //allowed extensions
    $allowedExts = array("xls", "xlsx");
    $extension   = end(explode(".", $_FILES["file"]["name"]));

    //check for allowed extensions
    if (in_array($extension, $allowedExts)){

      //check for file errors
      if ($_FILES["file"]["error"] > 0){
        echo "Return Code: " . $_FILES["file"]["error"] . "<br>";
        }
      else{
        //no error, upload file to directory
        echo "Upload: " . $_FILES["file"]["name"] . "<br>";
        echo "Type: " . $_FILES["file"]["type"] . "<br>";
        echo "Size: " . ($_FILES["file"]["size"] / 1024) . " kB<br>";
        echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br>";

        if (file_exists($upload_path . $_FILES["file"]["name"])){
          echo $_FILES["file"]["name"] . " already exists. ";
          }
        else{
          move_uploaded_file($_FILES["file"]["tmp_name"], $upload_path . $_FILES["file"]["name"]);
          echo "Stored in: " . $upload_path . $_FILES["file"]["name"];
          $isUploaded = true;
          }
        }
      }
    //invalid file extension, not allowed
    else{
      echo "Invalid file";
      }

    //on upload success
    if($isUploaded){
       //path to uploaded file
       $temp_path = $upload_path . $_FILES["file"]["name"];
    }
}
?>