PHP performs hash operation on files

This code is very useful. If you download a file and the website provides a hash result, you can perform a hash operation on the file you downloaded to verify whether the downloaded file is correct.

    Hash (Check) Files



             if(!empty($_FILES)){
            if ($_FILES["file"]["error"] > 0){
              switch($_FILES["file"]["error"]){
                  case 1:
                      echo "Error: The uploaded file exceeds the upload_max_filesize directive in php.ini";
                      break;
                  case 2:
                      echo "Error: The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.";
                      break;
                  case 3:
                      echo "Error: The uploaded file was only partially uploaded.";
                      break;
                  case 4:
                      echo "Error: No file was uploaded.";
                      break;
                  case 6:
                      echo "Error: Missing a temporary folder.";
                      break;
                  case 7:
                      echo "Error: Failed to write file to disk.";
                      break;
                  case 8:
                      echo "Error: A PHP extension stopped the file upload.";
                      break;
                  default:
                      echo "Unknown error occured.";
              }
            } else {
                echo 'Upload: ' . $_FILES['file']['name'] . '';
                echo 'Type: ' . $_FILES['file']['type'] . '';
                echo 'Size: ' . (round($_FILES['file']['size'] / 1024, 2)) . ' Kb';
                if(array_search($_POST['algo'], hash_algos())===false){
                    echo 'Unknown hashing algorithm requested.';
                } else {
                    echo 'Hashing Algorithm: '. $_POST['algo'] . '';
                    $hash = hash_file($_POST['algo'], $_FILES['file']['tmp_name']);
                    echo 'Calculated hash: ' . $hash . '';
                    if($_POST['exphash']!=='none' && !empty($_POST['exphash'])){
                        echo 'Expected hash:   ' . $_POST['exphash'] . '';
                        echo ($hash==$_POST['exphash'])? 'Hash matched expected value.' : 'Hash did not match expected value.';
                        echo '';
                    }
                }
            }
            ?>

            Again
                     }else {
    ?>


        Filename:


        Expected hash(optional):
        Choose an algorithm (This is the list of all the available algorithms in your php installation)

            foreach(hash_algos() as $algo){
                if($algo=='md5'){
                    echo "$algo";
                } else {
                    echo "$algo";
                }
            }
        ?>

             }
    ?>

php, hash