PHP文件上传失败求助：HTML与PHP均用name="file"却无效

Hey there, let's figure out why your file upload isn't working— I’ve spotted a few key issues in your code that are likely causing the problem:

1. The Form Isn’t Actually Submitting! #

Look at your submit button’s onClick handler:

<button type="submit" id="register-btn" onClick="register();return false;" ...>Submit</button>

The return false; here blocks the form’s default submit behavior. Even if you click the button, the form never sends data (including your file) to welcome.php.

Fix: #

Either remove the return false; entirely, or modify your register() function to return true only when validation passes (so the form submits when it should):

<button type="submit" id="register-btn" onClick="return register();" ...>Submit</button>

(Make sure your register() function returns a boolean value based on validation success.)

2. Your PHP Code Doesn’t Save the Uploaded File #

Right now, your PHP only checks if the file already exists—but it never actually moves the uploaded file from the server’s temporary directory to your uploads/ folder.

Fix: #

Add the move_uploaded_file() function after your checks. Here’s an updated version of your PHP code:

<?php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES['file']["name"]);
$uploadOk = 1;
$fileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));

// Check if file already exists
if (file_exists($target_file)) {
    echo "Sorry, file already exists.";
    $uploadOk = 0;
}

// If all checks pass, move the file
if ($uploadOk == 1) {
    if (move_uploaded_file($_FILES['file']["tmp_name"], $target_file)) {
        echo "The file ". htmlspecialchars( basename( $_FILES['file']["name"])). " has been uploaded.";
    } else {
        echo "Sorry, there was an error uploading your file.";
    }
}
?>

3. Additional Checks to Rule Out Other Issues #

• Directory Permissions: Make sure your uploads/ folder has write permissions for the web server. On most systems, setting permissions to 755 works (or 777 temporarily for testing, though 755 is more secure).
• PHP Configuration Limits: Check your php.ini file for these settings:
  • upload_max_filesize: Ensure it’s large enough for your files
  • post_max_size: Should be larger than upload_max_filesize
  • max_execution_time: Might need to increase if uploading large files
• Debugging Tip: Add var_dump($_FILES); at the top of your PHP script to see if the file data is even being received. If it’s empty, that confirms the form isn’t submitting correctly.

内容的提问来源于stack exchange，提问作者Salman Ashraf