Replace Magic Literal with Symbolic Constant

TL;DR

Explanation

Magic literals are unexplained values scattered through code. Types: magic numbers (if ($score > 42)), magic strings (if ($status === 'pnd')). Replace with: class constants (public const MAX_SCORE = 100), enums (Status::Pending), named constants (define('MAX_RETRIES', 3)), or config values. Benefits: single definition, searchable, self-documenting, single point to change. PHP: prefer class constants over global constants for scoping. Only exception: 0, 1, -1, true, false, empty string — universally understood.

Common Misconception

Why It Matters

Common Mistakes

• Using string literals for status values — use enums or class constants.
• Duplicating the same magic number in 10 places — one constant, 10 references.
• Creating constants with useless names: CONST_42 = 42.

Code Examples

if ($attempts > 3) { sleep(30); } // What are 3 and 30?
if ($status === 'pnd') { } // What is 'pnd'?

const MAX_RETRY_ATTEMPTS = 3;
const RETRY_DELAY_SECONDS = 30;

if ($attempts > MAX_RETRY_ATTEMPTS) { sleep(RETRY_DELAY_SECONDS); }

enum OrderStatus: string {
    case Pending = 'pending';
    case Complete = 'complete';
}

References

• ↗ https://refactoring.guru/replace-magic-number-with-symbolic-constant

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