Upload Max Filesize Exceeded

Why This Happens

PHP limits file uploads through two ini settings: upload_max_filesize controls individual file size and post_max_size controls total POST data size. When a file exceeds these limits, the upload silently fails and $_FILES['file']['error'] is set to UPLOAD_ERR_INI_SIZE (1).

The Problem

// php.ini: upload_max_filesize = 2M
$file = $_FILES['upload'];
move_uploaded_file($file['tmp_name'], '/uploads/' . $file['name']);
// Silently fails for files over 2MB

The Fix

$file = $_FILES['upload'];
if ($file['error'] !== UPLOAD_ERR_OK) {
    $errors = [
        UPLOAD_ERR_INI_SIZE => 'File exceeds upload_max_filesize',
        UPLOAD_ERR_FORM_SIZE => 'File exceeds MAX_FILE_SIZE',
        UPLOAD_ERR_PARTIAL => 'File was only partially uploaded',
        UPLOAD_ERR_NO_FILE => 'No file was uploaded',
    ];
    throw new RuntimeException($errors[$file['error']] ?? 'Upload error');
}
move_uploaded_file($file['tmp_name'], '/uploads/' . basename($file['name']));

Step-by-Step Fix

1. 1

   Check error code

   Always check $_FILES['file']['error'] before processing. UPLOAD_ERR_OK (0) means success; any other value is an error.

2. 2

   Increase limits if needed

   Set upload_max_filesize and post_max_size in php.ini. post_max_size must be larger than upload_max_filesize.

3. 3

   Add client-side validation

   Validate file size with JavaScript before upload to give users immediate feedback without waiting for the upload to complete.