php 文件上传问题

fdasf 2009-06-07 04:39:31

先上代码：



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">

<head>

	<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />

	<title>Upload an Image</title>

</head>

<body>

<?php # Script 11.1 - upload_image.php



// Check if the form has been submitted.

if (isset($_POST['submitted'])) {



	// Check for an uploaded file.

	if (isset($_FILES['upload']))   {



		// Validate the type. Should be jpeg, jpg, or gif.

		$allowed = array ('image/gif', 'image/jpeg', 'image/jpg', 'image/pjpeg');

		if (in_array($_FILES['upload']['type'], $allowed)) {

		

			// Move the file over.

			if (move_uploaded_file($_FILES['upload']['tmp_name'], "uploads/{$_FILES['upload']['name']}")) {

			

				echo '<p>The file has been uploaded!</p>';

			

			} else { // Couldn't move the file over.

			

				echo '<p><font color="red">The file could not be uploaded because: </b>';

		

				// Print a message based upon the error.

				switch ($_FILES['upload']['error']) {

					case 1:

						print 'The file exceeds the upload_max_filesize setting in php.ini.';

						break;

					case 2:

						print 'The file exceeds the MAX_FILE_SIZE setting in the HTML form.';

						break;

					case 3:

						print 'The file was only partially uploaded.';

						break;

					case 4:

						print 'No file was uploaded.';

						break;

					case 6:

						print 'No temporary folder was available.';

						break;

					default:

						print 'A system error occurred.';

						break;

				} // End of switch.

				

				print '</b></font></p>';



			} // End of move... IF.

			

		} else { // Invalid type.

			echo '<p><font color="red">Please upload a JPEG or GIF image.</font></p>';

			unlink ($_FILES['upload']['tmp_name']); // Delete the file.

		}



	} else { // No file uploaded.

		echo '<p><font color="red">Please upload a JPEG or GIF image smaller than 512KB.</font></p>';

	}

			

} // End of the submitted conditional.

?>

	

<form enctype="multipart/form-data" action="upload_image.php" method="post">



	<input type="hidden" name="MAX_FILE_SIZE" value="524288">

	

	<fieldset><legend>Select a JPEG or GIF image to be uploaded:</legend>

	

	<p><b>File:</b> <input type="file" name="upload" /></p>

	

	</fieldset>

	<div align="center"><input type="submit" name="submit" value="Submit" /></div>

	<input type="hidden" name="submitted" value="TRUE" />

</form>

</body>

</html>

我在本地测试，问题主要集中在红色那句话上。
比如，我不选择任何文件，直接点击提交，按我的理解，应该是$_FILES['upload']为空，那么页面应该显示Please upload a JPEG or GIF image smaller than 512KB.但实际测试下来却是显示Please upload a JPEG or GIF image.并且提示说unlink()出错，这说明$_FILES['upload']不为空。到底该怎么理解？
另外，我看到网上说表单中设置MAX_FILE_SIZE能限制上传文件的大小，但我故意用了个大文件来试，却没发现任何作用，这又该怎么理解？

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