<?
echo filesize($_POST['image_load']);
?>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>TEST</title>
<link href="style.css" rel="stylesheet" type="text/css">
<script type="text/javascript" src="jquery-3.2.1.min.js"></script>
</head>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>" id="buy_pixels">
<input type="file" name="image_load" id="image_load" value="" accept="image/*" required>
<input class="buy_button" type="submit" value="Buy" name="submit">
</form>
</body>
</html>
错误的原因是什么?