reference appendices

Magic Constants

Magic constants change value according to where PHP evaluates them. They are useful for diagnostics and path handling, but they should not replace explicit application configuration.

Use This Reference When

Building paths relative to the current file with __DIR__.
Logging source context with __FILE__, __LINE__, or __METHOD__.
Reading code that depends on namespace or trait context.

Inspect Context

PHP example

<?php

echo basename(__FILE__) . PHP_EOL;
echo __DIR__ . PHP_EOL;

// Prints the current filename and directory.

Common values include __LINE__, __FILE__, __DIR__, __FUNCTION__, __CLASS__, __TRAIT__, __METHOD__, and __NAMESPACE__.

Practice

Build a Relative Path

Use __DIR__ to build a path to a sibling config directory. Explain why it is safer than assuming the current working directory.

Show solution

Use $path = __DIR__ . "/config";. The current working directory can change according to the entry point or process manager; the source-file directory is stable.