Beginner terms
Undefined Array Key / Offset Errors
PHP 4.0+
Accessing a non-existent array key triggers E_WARNING (PHP 7) or is silently null (PHP 8 with nullsafe) — use isset(), array_key_exists(), or ?? to guard access.
3mo ago
php beginner
Undefined Variable and Null Coalescing Fixes
PHP 5.0+
Accessing an undefined variable in PHP returns null and triggers an E_WARNING — use isset(), empty(), or ?? to check safely before use.
3mo ago
php beginner
undefined vs null — Subtle Differences
ES5
undefined means 'not yet assigned' (declared but empty); null means 'intentionally absent' — they're different values but both falsy, and typeof null === 'object' is a famous JS bug.
3mo ago
javascript beginner
URL & URLSearchParams API
ES2015
URL and URLSearchParams provide structured URL parsing and query string building — the JavaScript equivalent of PHP's parse_url and http_build_query.
3mo ago
javascript beginner
Unreachable Code
PHP 5.0+
Code that can never execute because it follows a return, throw, exit, or an always-true condition — a sign of logic errors or forgotten cleanup.
3mo ago
quality beginner
Unused Function
PHP 7.0+
A function or method that is defined but never called — dead code that increases maintenance burden and confuses readers about what is part of the active API.
3mo ago
quality beginner
Unused Variable
PHP 5.0+
A variable that is assigned but never read — indicating a logic error, incomplete refactoring, or unnecessary computation.
3mo ago
quality beginner
Unit Testing
PHP 5.0+
1
Automated tests that verify individual units of code (classes, methods) in isolation from external dependencies.
3mo ago
testing beginner
UUID vs Auto-Increment IDs
1
UUIDs are globally unique identifiers that don't expose record counts or enable enumeration, at the cost of larger index size and random writes.
3mo ago
general beginner