PHP文件上传功能失效问题求助

Alright, let's break down why your upload script is always failing and fix it step by step. Your upload.inc.php has a couple of critical bugs, plus a few other things to verify even after fixing the code.

1. Case-Sensitive Variable Name Mistake #

PHP treats variables as case-sensitive, and you’ve got a typo here:

• You define $tempName = basename($_FILES["fileToUpload"]['tmp_name']); (capital N)
• But then you try to use $temp_name (lowercase n) in move_uploaded_file

Since $temp_name is never defined, the function gets an invalid path to the temporary upload file—this alone would cause the move to fail.

2. Duplicate move_uploaded_file Call #

You’re calling the move function twice in a row:

move_uploaded_file($temp_name, "$uploadsDir/$name");
if(move_uploaded_file($temp_name, "$uploadsDir/$name")) {

The first call already moves the temporary file to your uploads directory. By the time the second call runs, the temporary file no longer exists on the server—so it will always return false and trigger your error message.

Fixed upload.inc.php Code #

Here’s the corrected version with extra safeguards:

<?php
if(isset($_POST['submit'])) {
    $uploadsDir = '../uploads/';
    
    // Make sure the uploads directory exists (create it if not)
    if (!is_dir($uploadsDir)) {
        mkdir($uploadsDir, 0755, true); // Recursive create, 0755 is safer than 777
    }
    
    $name = uniqid() . '_' . basename($_FILES["fileToUpload"]["name"]); // Avoid filename conflicts
    $tempName = $_FILES["fileToUpload"]['tmp_name']; // No need for basename—tmp_name is a full path
    $error = $_FILES['fileToUpload']['error'];

    if ($error > 0) {
        echo "Error: " . $error . "<br />";
    } else {
        // Only call move_uploaded_file once
        if(move_uploaded_file($tempName, $uploadsDir . $name)) {
            echo "Successful";
            echo "Upload: " . $name . "<br />";
            echo "Stored in: Uploads Directory!";
        } else {
            echo "Did not move files!<br />";
            // Add debug info to see the exact error
            echo "Debug Details: " . error_get_last()['message'];
        }
    }
}
?>

Extra Checks to Rule Out Other Issues #

• Directory Permissions: Skip using 777 (it’s a security risk)—set your uploads directory to 0755 instead. Double-check that the server’s web process (like www-data for Apache or nginx for Nginx) has write access to the directory, not just "all users".
• PHP Upload Limits: Verify your php.ini settings:
  • file_uploads = On (file uploads are enabled)
  • upload_max_filesize is large enough for your files
  • post_max_size is larger than upload_max_filesize
• Filename Conflicts: The added uniqid() prefix ensures you don’t overwrite existing files with the same name, which would also cause move_uploaded_file to fail.

内容的提问来源于stack exchange，提问作者James