C - Vocabulary

The words that come up in PHP conversations and rarely anywhere else. One or two sentences each.

SAPI. Server API: the layer that connects the interpreter to whatever runs it. The command line, PHP-FPM, mod_php and the embedded runtimes are all SAPIs over the same engine.

CLI. The command-line SAPI, invoked as php file.php. It has no execution time limit and no memory limit by default, unlike the web SAPIs.

FPM. FastCGI Process Manager: a pool of PHP processes waiting for requests behind a web server. The standard way to serve PHP.

FastCGI. The protocol the web server uses to hand a request to FPM and read the response back.

mod_php. The Apache module that embeds PHP in the web server process itself. Older than FPM and still around.

OPcache. The bytecode cache. Compiled files stay in shared memory so the next request skips parsing. On in every serious setup.

JIT. Just-in-time compilation of hot code to machine code, inside OPcache, since 8.0. Helps CPU-bound scripts; changes little for typical web traffic.

Preloading. An OPcache option that compiles and links a set of files once at server start, so every request begins with them already loaded.

APCu. A memory cache shared between the PHP processes of one machine. For values you compute once and read often, when an external store is overkill.

Extension. A compiled C module that adds functions or classes to PHP: pdo_mysql, intl, mbstring, xdebug. php -m lists the loaded ones.

PECL. The historical repository of extensions not bundled with PHP, with its own installer.

PIE. The newer installer for extensions, Composer-style, meant to succeed the PECL workflow.

ZTS and NTS. Thread-safe and non-thread-safe builds of the interpreter. NTS is the default and the one FPM uses; ZTS exists for the rare threaded SAPIs and the parallel extension.

php.ini. The configuration file. The CLI and FPM read different ones, which explains most “it works in the terminal” mysteries.

Composer. The package manager. Reads composer.json, writes composer.lock, fills vendor/, generates the autoloader.

Packagist. The public package registry Composer fetches from.

vendor. The folder Composer installs packages into. Never edited, never committed.

Autoload. The mechanism that loads a class file the first time the class is used, so no require line is ever written by hand.

PSR-4. The standard mapping from namespace to folder that autoloaders follow: App\Billing\Invoice lives in src/Billing/Invoice.php.

PHP-FIG. Framework Interoperability Group: the body that publishes the PSRs and the coding style.

PSR. PHP Standards Recommendation: a numbered interface or convention (PSR-3 logging, PSR-7 HTTP messages, PSR-15 middleware) that libraries agree on so they can be swapped.

PER Coding Style. The current code style standard from the FIG, successor of PSR-12. What formatters enforce.

RFC. Request for Comments: the public proposal every language change goes through before a vote of the core developers.

PHP Foundation. The non-profit that, since 2021, employs core developers to maintain and advance the interpreter.

php-src. The source repository of the interpreter itself, written in C.

Zend Engine. The core of the interpreter: the compiler and the executor. The name survives in a few settings and error messages.

Superglobal. A built-in array visible in every scope: $_GET, $_POST, $_SERVER, $_COOKIE, $_FILES, $_SESSION, $_ENV.

Docblock. A /** ... */ comment above a symbol, carrying @param and @return annotations that editors and static analysers read. Where generics live.

Attribute. Structured metadata attached to a class, method, property or parameter with #[...], read through reflection. What annotations were in Java.

Trait. A block of methods and properties copied into any class that uses it. Horizontal reuse without inheritance.

Enum. A type with a fixed set of named cases, optionally backed by an int or a string, with methods and interfaces. Since 8.1.

Fiber. A stackful coroutine that can suspend and resume from anywhere in its call stack. The primitive async libraries build on; not something application code drives directly.

Generator. A function that yields values one at a time and keeps its state between calls. Lazy iteration without building an array.

SPL. Standard PHP Library: the bundled set of data structures, iterators, exceptions and interfaces such as ArrayIterator, SplQueue, Countable, RuntimeException.

PDO. PHP Data Objects: the database abstraction with one API over every driver, prepared statements included.

mbstring. The multibyte string extension. mb_strlen, mb_substr and friends count characters where the plain functions count bytes.

intl. The internationalisation extension: collation, number and date formatting, Unicode normalisation, wrapping the ICU library.

Xdebug. The step debugger and profiler. Development only.

PHPUnit. The xUnit-style test framework most PHP tests are written with.

Pest. A test framework with a describe-and-expect syntax, running on PHPUnit’s engine.

PHPStan. A static analyser that finds type errors and impossible code without running it, with levels from 0 to 10.

Psalm. The other static analyser, with levels from 8 down to 1 and a focus on type soundness and taint analysis.

Rector. An automated refactoring tool that rewrites code to a newer PHP version or a newer library API.

phpt. The test file format of the interpreter itself, in php-src. You meet it if you contribute to PHP or read its bug reports.

strict_types. The per-file declaration declare(strict_types=1); that makes scalar type mismatches on calls from that file throw instead of coerce.

Copy-on-write. The engine trick that makes array assignment cheap: the copy shares memory with the original until one of them is modified.

Late static binding. static:: resolving to the class the call was made on, not the class where the method is written. self:: is the other one.

Magic method. A method with a reserved double-underscore name that the engine calls on its own: __construct, __toString, __get, __call, __clone, __invoke.