Beginner terms
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.
4mo 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.
6mo 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.
6mo ago
Accessibility beginner
HTML Meta Tags
2
Tags in <head> that provide page metadata — title, description, viewport, Open Graph — for browsers, search engines, and social platforms.
6mo ago
Frontend beginner
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.
6mo 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.
6mo 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'.
6mo ago
PHP beginner
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.
6mo ago
Security beginner
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.
6mo ago
General beginner
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.
6mo 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.
6mo ago
Python beginner
Hardcoded Credentials
3
Secrets, passwords, or API keys embedded directly in source code can be extracted from repositories or compiled binaries.
CWE-798 OWASP A2:2021
6mo ago
Security beginner
9.8
Health Check Endpoints
PHP 5.0+
3
Dedicated endpoints that report application and dependency status, enabling load balancers, container orchestrators, and monitors to route traffic correctly.
6mo ago
DevOps beginner
Heredoc / Nowdoc
PHP 5.0+
Heredoc (<<<EOT) and Nowdoc (<<<'EOT') provide multi-line string syntax; Nowdoc is the single-quoted equivalent with no variable interpolation.
6mo ago
PHP beginner
HTML Forms — Validation & Accessibility
HTML5
1
Native HTML form validation, input types, and accessibility patterns — using browser built-ins before reaching for JavaScript.
6mo ago
Frontend beginner
HTML Injection
PHP 5.0+
1
Unsanitised user input rendered as raw HTML allows attackers to inject arbitrary markup, defacing pages or phishing users.
CWE-80 OWASP A3:2021
6mo ago
Security beginner
6.1
htmlspecialchars()
PHP 5.0+
1
Converts HTML special characters to entities — the primary defence against XSS in HTML output contexts.
6mo ago
PHP beginner
HTTP Security Headers
PHP 5.0+
1
A set of HTTP response headers that instruct browsers to enforce security policies, reducing XSS, clickjacking, and data leakage risks.
CWE-16 OWASP A5:2021
6mo ago
Security beginner
HTTP Status Codes
5
Three-digit codes in HTTP responses that indicate whether a request succeeded, failed, or requires further action.
6mo ago
Networking beginner
HTTP Strict Transport Security (HSTS)
PHP 5.0+
A response header that instructs browsers to always connect via HTTPS for a specified duration, preventing protocol downgrade attacks.
CWE-319 OWASP A5:2021
6mo ago
Security beginner