Fix PHP "Class Not Found"

Understanding the Error

Fatal error: Class 'ClassName' not found

Common Causes

1. Autoloader Issues (Composer)

# Regenerate autoloader
composer dump-autoload

# Check vendor folder exists
ls -la vendor/

2. Missing Include/Require

// Add the missing include
require_once '/path/to/ClassFile.php';

3. Namespace Issues

// Use full namespace
use Namespace\ClassName;

// Or backslash
$obj = new \Namespace\ClassName();

4. Case Sensitivity

Linux filesystems are case-sensitive:

// File: MyClass.php
class MyClass {}  // Exact case matters

5. Wrong PHP Version

Class may require newer PHP:

php -v
# Upgrade if needed

Debug Steps

# Check if file exists
ls -la /path/to/ClassFile.php

# Check file permissions
stat /path/to/ClassFile.php

# Verify syntax
php -l /path/to/ClassFile.php

WordPress Class Not Found

# Reinstall WordPress core
wp core download --force

# Check plugin compatibility
wp plugin status