Terms starting with "R"
Regex Conditional Patterns
PHP 4.0+
1
Conditional regex constructs like (?(1)yes|no) match different subpatterns depending on whether an earlier group captured.
2d ago
regex advanced
Register Allocation
PHP 8.0+
6
A compiler back-end pass that maps an unbounded set of virtual registers (or IR variables) to a finite set of physical CPU registers.
4d ago
compiler advanced
Regex Branch Reset Groups
A PCRE-specific construct (?|...) that resets capture group numbers across each alternative, so all branches share the same group indices.
4w ago
regex advanced
Reasoning Models & Test-Time Compute
A class of LLMs trained to allocate extra inference-time compute to internal reasoning before answering, achieving large gains on math, code, and logic at the cost of latency and tokens.
1mo ago
ai_ml intermediate
RLHF — Reinforcement Learning from Human Feedback
Post-training method where human preference rankings train a reward model that fine-tunes an LLM via reinforcement learning, aligning outputs with human preferences.
1mo ago
ai_ml advanced
Recursive Types
3.7 Types that reference themselves to describe arbitrarily nested structures — trees, nested menus, JSON, linked lists — without requiring any escape hatch.
2mo ago
typescript advanced
Resource Hints (preconnect, prefetch, preload)
HTML link attributes that instruct the browser to take early action on resources — opening connections, fetching future pages, or loading critical assets before they are discovered in HTML parsing.
2mo ago
performance intermediate
RabbitMQ Concepts
RabbitMQ is an AMQP message broker with flexible routing via exchanges — direct, topic, fanout, and headers routing enables complex message dispatch patterns.
2mo ago
messaging intermediate
RabbitMQ Fundamentals
PHP 7.0+
A message broker implementing the AMQP protocol — producers publish to exchanges, exchanges route messages to queues via bindings, and consumers pull from queues — providing flexible routing, acknowledgements, and dead-letter handling.
2mo ago
messaging intermediate
Race Condition
1
A race condition occurs when the outcome of a program depends on the relative timing of concurrent operations — two threads reading and writing shared state without coordination.
2mo ago
concurrency intermediate
Raft Consensus Algorithm
A consensus algorithm designed to be understandable — Raft elects a leader who coordinates all writes, replicates log entries to followers, and ensures that committed entries are never lost even when servers fail.
2mo ago
architecture advanced
RAG — Retrieval-Augmented Generation
An LLM architecture that fetches relevant documents from an external knowledge base before generating a response, grounding answers in retrieved facts rather than training data alone.
2mo ago
ai_ml intermediate
readonly Classes (PHP 8.2)
PHP 8.2+
PHP 8.2 readonly classes make all promoted properties readonly automatically — the cleanest way to define immutable value objects and DTOs.
2mo ago
php beginner
readonly Properties (PHP 8.1)
PHP 8.1+
PHP 8.1 readonly properties can only be written once (in the constructor) — enforcing immutability without verbose accessor boilerplate.
2mo ago
php beginner
Redis
PHP 7.0+
An in-memory key-value data store used in PHP applications for caching, session storage, queues, rate limiting, and pub/sub — providing sub-millisecond data access compared to database queries.
2mo ago
performance beginner
Reducing Cyclomatic Complexity Techniques
Cyclomatic complexity counts independent code paths — reduce it by early returns, extracting conditions to named functions, using lookup tables, and replacing switch/if chains with polymorphism.
2mo ago
quality intermediate
Refactoring Boolean Flag Parameters
Boolean flags as function parameters obscure intent — replace with enums, separate functions, or named options objects for self-documenting APIs.
2mo ago
quality intermediate
Regex Flags (i, g, m, s, x, u)
PHP 5.3+
Modifiers appended to a regex pattern that change matching behaviour — case-insensitivity, multiline mode, dotall mode, extended whitespace, and Unicode awareness.
2mo ago
regex beginner
register_globals Era & Why It Was Dangerous
PHP 3.0+
PHP 4 shipped with register_globals=On by default — injecting GET/POST/COOKIE values as global variables, making PHP synonymous with insecurity until it was off-by-default in PHP 4.2.
2mo ago
php intermediate
Remote Code Execution (RCE)
A vulnerability allowing an attacker to run arbitrary code on the server — the most severe class of web vulnerability, typically achieved through eval(), unserialise(), file upload flaws, or OS command injection.
2mo ago
security intermediate