up.php
<!DOCTYPE html>
<html lang="ja">

<head>
  <meta charset="UTF-8">
  <title>img_upload</title>
</head>

<body>

  <?php
  var_dump($_FILES['file']);
  
  $filename =  './img/'.date('Y-m-d H:m:s') . '.jpg';

  if ($_FILES['file']) {
    move_uploaded_file($_FILES['file']['tmp_name'], $filename);
    
  }
  echo "<img src = '$filename'>"
  ?>
//enctypeは決まり文句
  <form action="up2.php" method="POST" enctype="multipart/form-data">
    <input type="file" name="file" accept="image/*">
    <input type="submit" value="ファイルをアップロードする">
  </form>

  


</body>

</html>