PHP and framework glossary#

These are the terms used throughout the Elang learning path. You do not need to memorize them before building your first page; come back when a term becomes useful.

PHP#

PHP is the programming language that executes the backend code. Elang is a framework written in PHP. Installing Elang does not install a new programming language or a separate interpreter.

Framework#

A framework provides conventions and reusable tools for building applications. Elang coordinates requests, routes, services, and responses. Your own application still defines its features, data model, and access rules.

Backend and frontend#

The backend runs on the server. It reads input, applies rules, accesses data, and creates responses. The frontend is what the browser displays and interacts with: HTML structure, CSS presentation, and JavaScript behavior. This site uses Elang on the backend and plain HTML, CSS, and JavaScript on the frontend.

HTTP request and response#

A request asks the server to do something. It includes a method, URL, headers, and sometimes a body. A response includes a status, headers, and usually a body. A JSON API and an HTML page use the same underlying exchange.

HTTP method and status code#

GET reads a resource; POST commonly submits data or creates something. PUT, PATCH, and DELETE express other changes when your API defines them. Status codes communicate the result: 200 is success, 201 is creation, 404 means not found, and 422 can identify validation failures.

Route#

A route maps a method and path to a handler. /posts/{id} contains a named parameter. A named route also has an internal label used to generate a URL without repeating its path throughout the application. See routing.

Controller#

A controller is a class containing request-handling behavior. It can accept injected services, read a request, validate input, and return a response. It helps keep the route file readable as an application grows.

Middleware#

Middleware wraps the next step of a request. It can inspect input, reject a request, or change a response. Order matters: session middleware must establish the session before CSRF middleware checks a token stored in it.

Service and dependency injection#

A service is an object that performs a useful job, such as rendering a template or connecting to a database. Dependency injection supplies that object through a constructor or handler parameter, rather than asking application code to create every dependency itself.

Container and singleton#

The container resolves services. A normal binding or unbound concrete class produces a fresh object. A singleton binding reuses one object within that application instance. A request-dependent object should not accidentally become a long-lived shared service.

Composer and package#

Composer installs a project's PHP libraries and creates its autoloader. A package is a reusable library described by composer.json. Composer resolves versions and records the chosen versions in composer.lock. It does not make every package globally available to every PHP project.

Namespace and autoloading#

A namespace gives a class a qualified name such as App\Controllers\HelloController. Composer's PSR-4 mapping connects that name to a file. A use statement imports a name for readability; it does not install a missing package.

Environment variable and configuration#

Environment-specific values include database credentials, the canonical site URL, and an application key. Elang reads these through configuration. The .env file must remain outside the public directory and out of version control.

Validation and escaping#

Validation decides whether input is acceptable for a particular purpose. Escaping encodes output safely for a specific context. A title can be valid text while still containing < or &; Twig escapes those characters when rendering HTML. Validation and escaping solve different problems.

Database, query builder, and ORM#

A database stores records. A query builder constructs SQL through an API, but user values must still be bound as parameters. An ORM maps records to domain objects and adds a different set of abstractions. Elang currently includes Doctrine DBAL and a query builder, not a built-in ORM.

Migration and transaction#

A migration changes database schema in a versioned file. A transaction groups compatible operations so they can commit together or roll back after a failure. Database engines differ in how schema changes interact with transactions; MySQL DDL can implicitly commit.

Session and cookie#

A session stores server-side data associated with a browser. A cookie carries the session identifier. A session is useful for temporary state, but it does not automatically establish a user's identity. A login system needs additional authentication and authorization behavior.

CSRF#

Cross-site request forgery tricks a browser into making a state-changing request with its existing cookies. A CSRF token connects a form submission to the intended session. It does not protect an API that has no authorization rules or make unsafe data valid.

Authentication and authorization#

Authentication establishes who the caller is. Authorization decides what that caller may do. Hashing a password is only one primitive used by an authentication system. Auth Starter provides account flows, while each application must still define ownership checks and access policies.

Cache and log#

A cache temporarily stores reusable results. A log records server-side events and errors for diagnosis. Neither should be placed in the public directory. Avoid logging secrets or assuming a cached value stays valid forever.

CLI and document root#

CLI means command-line interface: commands run in a terminal, such as php elang doctor. The document root is the directory a web server exposes. For Elang it should be public/, while source, vendor files, configuration, and storage remain private.

Next step#

Apply the vocabulary in your first route, or follow the complete task board project to see several concepts working together.