PHP constants are named values declared by const or define().
What It Does
PHP constants are named values declared by const or define(). The following examples distinguish a normal use case, a boundary case and a practical application.
Requirements and Compatibility
PHP 8.x and a local test environment. Apply input validation, correct error handling and the requirements of any optional libraries.
The code focuses on the core concept. Production implementation may also need routes, validation, persistence, authorization or deployment tooling.
Example 1: Basic Behavior
Start with the smallest meaningful working case.
<?php
define('APP_TITLE', 'Sample Portal');
echo APP_TITLE;Example 2: Another Case
Examine the edge case and the observable result.
<?php
const MAX_ITEMS = 40;
echo MAX_ITEMS;Practical Example: Putting It to Use
Apply the technique to a small practical task.
<?php
final class ApiLimits { public const PAGE_SIZE = 25; }
echo ApiLimits::PAGE_SIZE;Important Behavior and Edge Cases
Constants should represent stable configuration and must not be confused with secrets loaded at runtime.
Comparison with Related Functions or Approaches
| Option | What it means in practice |
|---|---|
| Constants and define() | PHP constants are named values declared by const or define(). |
| Related approach | Class constants scope related values within classes or enums. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Ignoring the important boundary for Constants and define() | Constants should represent stable configuration and must not be confused with secrets loaded at runtime. |
| Assuming a related mechanism has the same behavior | Class constants scope related values within classes or enums. |
Key Takeaways
- PHP constants are named values declared by const or define().
- Constants should represent stable configuration and must not be confused with secrets loaded at runtime.
- Class constants scope related values within classes or enums.
Before adapting these examples, verify the return values, test the failure paths and confirm that your application meets its security and environment requirements.