Quick Answer

Resolve missing class declarations.

Understanding the Issue

This fatal error occurs when trying to use a class that PHP cannot locate, typically due to missing includes or namespacing issues.

The Problem

This code demonstrates the issue:

Php Error 
<?php
$obj = new UndefinedClass(); // Fatal error

The Solution

Here's the corrected code:

Php Fixed 
<?php
// Solution 1: Include class file
require "UndefinedClass.php";

// Solution 2: Use autoloading
spl_autoload_register(function ($class) {
    include "classes/" . $class . ".php";
});

// Solution 3: Check namespaces
use MyNamespaceUndefinedClass;

Key Takeaways

Ensure proper file inclusion or implement autoloading.