Terms starting with "H"
Heading Hierarchy (h1-h6)
Headings must form a logical, sequential outline (h1 then h2, no skipped levels) so screen reader users can navigate and grasp page structure.
3w ago
Accessibility beginner
HTTP Cookies in PHP
PHP 7.3+
3
Cookies are small key-value pairs sent by the server via Set-Cookie and echoed back by the browser on every request — PHP sets them with setcookie() before any output, with Secure, HttpOnly, and SameSite flags controlling safety.
3mo ago
PHP beginner
HTML lang Attribute
The lang attribute on <html> declares the page's primary language — required for screen readers to select the correct voice profile and pronunciation rules, and for WCAG 2.1 compliance.
3mo ago
Accessibility beginner
HTML Meta Tags
1
Tags in <head> that provide page metadata — title, description, viewport, Open Graph — for browsers, search engines, and social platforms.
3mo ago
Frontend beginner
HTTP Content Negotiation
1
The HTTP mechanism by which clients declare what formats, languages, and encodings they accept (Accept, Accept-Language, Accept-Encoding) and servers respond with the best match — or 406 Not Acceptable if none fits.
3mo ago
API Design intermediate
HTTP/2 Server Push & Early Hints
2
HTTP/2 Server Push lets a server proactively send assets (CSS, JS, fonts) before the browser requests them. 103 Early Hints is its practical successor — sending Link preload headers before the full response is ready.
3mo ago
Networking intermediate
Health Check Patterns
Health checks report service status to load balancers and orchestrators — /health/live (is the process running?), /health/ready (can it serve traffic?), and deep health checks for dependencies.
3mo ago
Observability beginner
HTTPS & TLS
HTTP over TLS — encrypts all traffic between browser and server, preventing eavesdropping, man-in-the-middle attacks, and tampering. Required for cookies, modern APIs, and all production web applications.
3mo ago
Security beginner
Headers Already Sent Error
PHP 5.0+
1
PHP sends HTTP headers on first output — any echo, whitespace, or BOM before header() causes 'Cannot modify header information — headers already sent'.
3mo ago
PHP beginner
Hoisting — var, let, const and function
ES5
JavaScript hoists declarations to the top of their scope — var and function declarations are fully hoisted, while let and const are hoisted but remain in the Temporal Dead Zone until their declaration line.
3mo ago
JavaScript intermediate
History API — SPA Routing with PHP Backend
HTML5
history.pushState and popstate enable URL changes without page reload — used for SPA routing while keeping PHP as the backend.
3mo ago
JavaScript intermediate
Hardcoded Credentials
PHP 5.0+
Passwords, API keys, or tokens written directly into source code — permanently exposed to anyone with repository access and impossible to rotate without a code change.
3mo ago
Security beginner
Hashing Algorithms Deep Dive
PHP 7.2+
Comparing hash functions for different use cases — MD5/SHA-1 (broken, legacy), SHA-256/BLAKE3 (data integrity), bcrypt/Argon2 (passwords), xxHash/MurmurHash (non-cryptographic, fast).
3mo ago
Algorithms intermediate
Hofstadter's Law
"It always takes longer than you expect, even when you take Hofstadter's Law into account" — software estimation is systematically and recursively optimistic.
3mo ago
General beginner
How CDNs Work
1
CDNs use Anycast routing and distributed edge PoPs to serve content from the nearest location — reducing latency from 300ms to 5ms for cached responses.
3mo ago
Networking intermediate
HTML Meta Tags & SEO
PHP 5.0+
1
Essential meta tags for search engine visibility and social sharing — title, description, canonical, Open Graph, Twitter Card, and structured data.
3mo ago
Frontend beginner
HTTP in Python — requests & httpx
Python 3.7+
requests is the standard sync HTTP library; httpx adds async support, HTTP/2, and a similar API — both far more ergonomic than urllib.
3mo ago
Python beginner
HTTP Request-Response Cycle
3
The complete lifecycle of an HTTP request — DNS resolution, TCP connection, TLS handshake, request transmission, server processing, and response delivery.
3mo ago
Networking intermediate
HTTP/3 & QUIC
HTTP/3 runs over QUIC (UDP-based) instead of TCP — eliminating head-of-line blocking, reducing connection setup time, and improving performance on lossy networks.
3mo ago
Performance advanced
Hypermedia APIs — HATEOAS
REST APIs that include links in responses — clients discover available actions from the response rather than hardcoding URLs, making APIs self-describing and evolvable.
3mo ago
API Design advanced